Assembling Portable Cribs and Adjusting Shtenders on Shabbos

Since the parsha tells us that the Jews were enslaved
to perform many construction projects, this is an appropriate week to analyze
the halachos of construction on Shabbos.

Question #1: I am having a lot of company for Shabbos
and we have a small house. On Friday night, I would like to remove the extra
leaves from the table and then set up the “portacrib” in the space that
creates, and then, in the morning, fold up the crib and put the table leaves
back. May I do this on Shabbos?

Question #2: The lens fell out of my eyeglasses on Shabbos.
May I pop it back in?

Question #3: I have an adjustable shtender that I
usually leave at the same height. May I adjust it on Shabbos?

Question #4: The house is very crowded and stuffy because we
are celebrating a kiddush. May I remove a door or a window to allow some
additional ventilation? (I was asked this shaylah in Israel where doors
and windows are hinged in a way that they are easily removable.)

Question #5: May I remove the pieces of glass from a broken
window on Shabbos?

Before discussing these shaylos, we need to explain
the halachos of construction on Shabbos, and how they apply to
movable items such as household furnishings and accessories.


Boneh, building or constructing, is one of the 39 melachos
of Shabbos. Included in this melacha is performing any type of
home repair or enhancement, even only a minor repair (see Shabbos 102b).
Thus, it is prohibited min haTorah to hammer a nail into a wall in order
to hang a picture (Rashi, Eruvin 102a s.v. halacha). Similarly,
one may not smooth the dirt floor of a house because this enhances the
“structure” (Shabbos 73b).

Sosair, demolishing or razing, is also one of the 39 melachos,
since the Bnei Yisroel disassembled the mishkan whenever they
moved from place to place (Shabbos 31b). Therefore, any demolition of a
building is prohibited min haTorah if the ultimate results are
beneficial, such as the razing of part of a building in order to renovate it.

If there are no benefits to the demolition, it is still
prohibited miderabbanan. Thus, wrecking the house out of anger violates Shabbos
only miderabbanan (according to most Rishonim) since there is no
positive benefit from the destruction (Pri Megadim 314:11 in Eishel
). It is prohibited min haTorah because of other reasons,
such as bal tashchis (unnecessary destruction) and being bad for one’s midos
(see Shabbos 105b).

We already have enough information to address questions #4
and #5 above, whether one may remove a window to ventilate the house and
whether one may remove pieces of glass from a broken window. It would seem that
the first case is prohibited min haTorah since it involves the melacha
of sosair for positive results. The second case may depend on whether
the removal of the broken glass is so that no one hurts himself, in which case
this might be prohibited only because of a rabbinic injunction, or whether it is
being removed as the first step in the repair, in which case it would be
prohibited min haTorah.

If the broken window is dangerous (but not life
threatening), I may ask a non-Jew to remove the broken pieces of glass.


Do the melachos of boneh and sosair apply
to movable items, keilim (sing., kli), as well, or only to
buildings? In other words, does the Torah’s prohibition refer only to something
connected to the ground, or does it include construction of a movable item?

This question is disputed in the Gemara and by the Rishonim
(Beitzah 10a). There are three basic opinions:

1. Keilim are not included in the prohibition of boneh
and sosair.

2. Keilim are totally included in the prohibition of boneh
and sosair.

3. A compromise position in which total construction or
destruction of a kli is prohibited min haTorah, but minor
improvement is not (Tosafos, Shabbos 74b and 102b). The halacha
follows this opinion (Shulchan Aruch Orach Chayim 314:1).


Assembling or improving a kli in a way that involves
strength and skill constitutes boneh, and disassembling it involves sosair.
Therefore, it is prohibited min haTorah to assemble a piece of furniture
in a way that tightens the pieces since this involves strength and skill to do
the job properly. Similarly, replacing the handle on a hoe or other appliance
is prohibited min haTorah since it requires skill and strength to do the
job properly (Shabbos 102b).

Assembling furniture without tightening the pieces is not
prohibited min haTorah, but is prohibited miderabbanan out of
concern that one might tighten them (Tosafos, Shabbos 48a s.v. ha;
Hagahos Ashri
Shabbos 3:23). Therefore, one may not assemble a bed,
crib, or table even without tightening the pieces (Kaf Hachayim 313:63).

To review:

One may not assemble a crib on Shabbos. Assembling it
in a tight way is prohibited min haTorah, whereas assembling it without
tightening the pieces is prohibited miderabbanan since one might
assemble it tightly.

However, the halacha regarding the setting up of
portacribs is lenient, since this does not involve re-assembling. Everything
remains attached and the parts are merely straightened out. So they can
certainly be opened and closed on Shabbos.


Repairing a broken appliance on Shabbos follows the
same guidelines as assembling. Therefore it is prohibited when the repair
requires skill and strength even if one repairs it in a temporary way.

Therefore, if the leg of a bed or table fell out, one may
not reinsert it even temporarily out of concern that one might repair it
permanently (Shulchan Aruch Orach Chayim 313:8). In this instance,
decreed that the bed or table itself becomes muktzah in order
to ensure that someone does not repair it (Rema Orach Chayim 308:16).


There are two exceptions to this rabbinic prohibition, when
one may assemble or repair an item in a non-permanent way. The first is on Yom
where the halacha is that one may use a temporary repair to fix
a furniture item for a Yom Tov need (Tosafos, Beitzah 22a; Shulchan
Aruch Orach Chayim
519:2, Magen Avraham and Gra ad loc.).


A leg fell off the table on Yom Tov. Repairing the
table in a proper way is prohibited min haTorah, and therefore on Shabbos
I may not even reinsert the leg into the table in a temporary way.  On Yom
, however, I may reinsert the leg without performing a proper repair, if
this is the most convenient table to use.


If the broken or disassembled item is usually repaired or
assembled without strength or skill, I may repair it in a temporary fashion. Chazal
did not forbid this since it is unlikely that it will cause any Torah violation
(Shabbos 47b with Tosafos).


In the time of the Gemara there existed a type of bed
called “a coppersmiths’ bed.” Apparently, it was common that coppersmiths
traveled from place to place making their living as iterant repairmen, and took
portable beds with them that they reassembled at each destination. May one
assemble this bed on Shabbos or is it considered construction? The
quotes a dispute on the subject. According to the Tanna who
contends that keilim are totally included in the prohibition of boneh
and sosair, one may not assemble these beds on Shabbos (Shabbos

However, the conclusion of the Gemara is that one may
assemble these beds on Shabbos. That is because these beds were never
assembled very tightly and therefore it is not considered boneh to construct
them, nor does it qualify as a rabbinic prohibition. However, an appliance that
is normally assembled very tightly would be prohibited to assemble even loosely
since it might be tightened (Tosafos ad loc.).


Inserting table leaves also does not require skill or
strength and is therefore permitted on Shabbos. However, some tables
have a clamp to tighten the table after inserting or removing the leaf. Some
authorities contend that tightening this clamp might be prohibited min
. Those who hold that way will also prohibit adding or removing
leaves from these tables on Shabbos, even if one does not tighten the
clamp, out of concern that one might tighten it.


About three hundred and fifty years ago, the poskim
began discussing appliances held together with screws. Around this time a
drinking cup became available where the cup part screwed into a base. Does
screwing this appliance together on Shabbos constitute boneh?

The halachic question here is as follows: Although
this cup does not require someone particularly strong or skilled to assemble
and disassemble, screwing on the base makes the cup into a well-made permanent
appliance. Thus, the screw enables someone who is not particularly skilled to build
a strong appliance.

The early poskim debate this issue. The Magen
(313:12) rules that screwing an appliance together constitutes a melacha
min haTorah (see Shaar Hatziyun 313:32); the Maamar Mordechai
disagrees. In practice however, the Maamar Mordechai concludes that one
should follow the stringent ruling of the Magen Avraham, and this is the
accepted halachic practice. Thus, screwing the cup together is considered
manufacturing a cup.

Similarly, today you can purchase furniture that you take
home and assemble by yourself. Assembling this furniture is prohibited min
even though it is made in a way that an unskilled person can
assemble it. Thus, the definition of “skill and strength” is not whether the
assembler needs to be skilled or strong, but whether the appliance thereby made
is a permanent, well-made appliance.


Focusing a pair of binoculars involves turning a screw to
make it tighter and looser. Does this violate boneh on Shabbos?

The poskim rule that one may focus binoculars on Shabbos
(Kaf Hachayim 313:73; Ketzos Hashulchan 119:12). They explain
that there is a qualitative difference between screwing the base onto the cup,
which creates an appliance, and screwing the binoculars, which is the method of
using it. One may use an appliance, just as one may use a house by opening and
closing the doors and windows. This is not considered building an extension
onto the house, but normal daily usage.


Many shtenders are tightened and loosened by the use
of a screw. May one adjust ashtender by loosening and tightening the

According to Rav Shlomo Zalman Auerbach and Rav Vozner, one
may adjust the height of the shtender on Shabbos since this is
considered using the shtender, not making a new appliance (Shulchan
313:7; Shu”t Shevet Halevi 6:32; cf. Shu”t Minchas
9:38, who prohibits).



I forgot to fill the saltshaker before Shabbos, and
now I realize that it is empty. May I unscrew the saltshaker on Shabbos
to fill it, or is this considered demolishing and repairing the saltshaker?

Rav Shlomo Zalman Auerbach rules
that it is permitted to open, refill, and close the saltshaker on Shabbos
without violating boneh. Although the saltshaker is indeed screwed
closed, it is typically not screwed as tightly as one screws furniture or the
cup we described earlier (Minchas Shlomoh 1:11:4 s.v. gam nireh).

A similar halacha, although
for a different reason, applies to opening and closing a baby bottle. Although
it is opened and closed by screwing, since it is intended to be opened and
closed constantly, it is not considered demolishing and reconstructing it.


If someone’s eyeglass lens falls out on Shabbos, may
he reinsert it back into the glasses?

It would seem that it depends on the type of eyeglasses. In
glasses where the lens is held in place simply by placing the lens in the
frame, one may pop the lens back into place. This is because placing the lens
into the glasses cannot constitute boneh since it does not require

However, there are some frames
that tighten around the lens with screws. According to the Magen Avraham,
it would seem that tightening the screws to hold in the lens involves a Torah
prohibition of boneh. If that is true, then one may also not pop the
lens because of concern that one might screw the frame tight.


We may ask ourselves, why is
screwing a cup together or removing a window from its hinge considered melacha?
They take a second to do and are not at all strenuous.

Rav Samson Raphael Hirsch (Shemos 20:10) notes that
people mistakenly think that work is prohibited on Shabbos so that it
should be a day of rest. He points out that the Torah did not prohibit doing avodah,
which connotes hard work, but melacha, which implies purpose and
accomplishment. Shabbos is a day that we refrain from constructing and
altering the world for our own purposes. The goal of Shabbos is to allow
Hashem’s rule to be the focus of creation by withdrawing from our own creative
acts (Shemos 20:11). By restraining from building for one day a week, we
demonstrate Who indeed is the Builder of the world and all it contains.