Building and Destroying: How Goodly are Your Tents? (III)

Now we can discuss a few practical cases.  The first case is the umbrella.  According to the third approach above, it would seem to be an open and shut case.  An umbrella is clearly pre-made and collapsible.  It would seem from here that it would be permitted.  While the Chazon Ish follows this line of reasoning, he rules in practice that it is prohibited due to it’s looking like a non-Shabbos activity.  (However there are those that rule that it is a biblical prohibition.)

The next case would be holding a talis over the heads of people.  While it would seem to be prohibited because it is used for shade, it seems to be explicitly permitted in the gemara.  This is the case mentioned above that one may first hold a talis and then stand up beds to support it.  The gemara assumed that it was obvious that it is permitted to hold the talis for shade.

The last case is covering a crib with a blanket.  This is clearly prohibited because one is creating a protective tent over the crib.  However it would be permitted if there was already a tefach of blanket spread before shabbos.

Building and Destroying: How Goodly are Your Tents? (II)

Even though it is prohibited to make a halachic tent, there are various cases in which is could be allowed.  The first is mosif al ohel array.  This means that it is permitted to make a temporary addition to an already existing ohel.  This can be done in one of two ways.  The first is that if you have a tefach (between 8 and 10 cm) of covering, it is permitted to extend it.  The second is that if one has an ohel using the halachic principle of lavud, you can fully cover it.  This means that if one has an open roof, but it has cross beams (or even fine string) stretched across it, at intervals of less than three tefachim, you can cover over the space.  According to the Mishna Brurah one can combine these two concepts, and even if there is only one place that has two cross beams within three tefachim, but covering a total of more than one tefach, one can extend from this to cover the entire area.

The second way in which it is mutar to make an ohel is melma’aleh lemateh.  This means that if first one builds the top, and then one brings the wall, it is mutar to make.  While I do not have a clear proof, it seems to me that this would apply even with an ohel without walls.  If you bring the top before the supports, I believe that it would also be mutar.  The proof for this is a gemara that discusses making a covering over a dead person to protect from the sun.  The gemara says that one may hold a talis over his head, and then bring standup beds to support the talis.  The last way in which it is mutar to make an ohel is avid v’kay.  This means that any ohel that is not made out of parts, rather is collapsible, is mutar to put up on shabbos.

Building and Destroying: How Goodly are Your Tents?

The last toldah of binyan is ohel, tent.  The d’Oraysa is to create a permanent halachic tent; however, the more practical aspect is ohel array , the rabbinic prohibition to create even a temporary halachic tent.

The first thing that must be defined is the definition of a halachic tent.  Firstly, a vertical partition is not considered a tent unless it serves as a halachic border.  (An example would be a third wall for a suka or a partition to create a private domain.  A partition between men and women during prayer would be permitted to make.)  Secondly, even a horizontal partition is only prohibited if either it is made to protect the area underneath, or it is made to use the area underneath.  A table would be permitted to make, even though it covers a space, because the main use of a table is to eat on top and not to put things underneath.  Even so, we assume that any covering with four walls is prohibited because one can put things underneath.

Building and Destroying: Can I?

This week I want to discuss opening tin cans on shabbos.  At first glance, it is very simple.  We have a mishna that says that you can break a barrel to gets its contents.  So it’s allowed!  It is more complicated than that because the Shulchan Aruch rules in accordance with Tosfos.  If so, it is only permitted to break a barrel if it is a mustaki.  Based on this, it would seem that it is prohibited to open a tin can, because they are made out of sturdy material.  Even so, today’s poskim originated an idea that would make even a tin can be considered a mustaki.  They said that anything that one is going to throw away, even though it technically is a solid vessel, will not have a rabbinic prohibition because we are not worried that you will try to make a neat opening.  Based on this, one can conclude that it is permitted to open a tin can on shabbos,  as long as one does not intend to make a neat opening.

However, many poskim take a more stringent approach.  This is based on a ruling by the Chazon Ish that a sealed tin can is not considered a vessel at all because you cannot put anything into it, or take anything out of it; therefore, when you open it, you effectively create a whole new vessel.  There are two ways to avoid this problem.  The first is by making a hole in the bottom of the can before opening the top.  In this way, there never is a usable vessel.  (However some poskim are concerned by issues of borer, something that is beyond the scope of this post.  I hope in a few months to revisit this issue.)  The other possibility is that even the Chazon Ish was only talking about a situation in which it was common to reuse cans, due to extreme poverty.  Today, when everyone throws them away immediately, even he would concur that it is permitted.