פירוש על כלים 22:3

ספסל – a wide and long board/plank, its one end/head/ is fastened with a a high board/plank and similarly its second head/end, in order to left it up from the group that it would be appropriate to sit upon.

A bench, one of whose legs was removed, is clean. If its second leg also was removed it is still clean. If it was one handbreadth high it is unclean. A bench has two legs, one on either end. Clearly if one leg is removed, the bench cannot be used and it is pure. The same is true even if both legs are removed. One does not sit on a bench when it is simply a board on the ground, because it is usually too thin. However, if the bench-board is at least one handbreadth high, it is unclean because a person might come to sit on it.

ניטל השני טהור – for it is not similar to a table that if the removed three legs it is impure, for a bench whose two ends/heads were broken is not appropriate for sitting, for a person who sits upon it is like sitting on the ground.

A footstool one of whose legs was removed is unclean. A footstool can be used to put one's feet up even if one of the legs has been removed. In other words, a footstool does not have to be exactly upright because one doesn't sit on it. Therefore, since it can fulfill its original function, it remains unclean (or susceptible to impurity).

אם יש בו גובה טפח אמא – that the board/plank is a handbreadth thick it is appropriate for sitting.

The same applies to the stool in front of a cathedra. A "cathedra" is a couch used by the upper class (same word as cathedral). The stool in front of it has the same rule as does a footstool.

שרפרף (a sort of camp stool/footstool) – a bench for the footstool of a person.

הכסא שלפני קתדרא (stool that is before the throne/chair with a back) – its law is like that of a footstool.