928. Protrusions Extending From a Wall

Eiruvin 3:5

Let’s say that one builds a platform over another platform on the side of a wall between two courtyards. If the lower platform is four handbreadths high (about a foot), we act as if the height of the wall were reduced; if it is not four handbreadths high but there are fewer than three handbreadths (about 9”) between the two platforms, we act as if the height of the wall were reduced. In either of these cases, the residents of the two courtyards have the option to make a single eiruv. The same is true when there are wooden steps next to a wall.

Eiruvin 3:6

Let’s say that there’s a tall wall in between two courtyards and some protrusion extends from the middle of the wall. If there are fewer than ten cubits (about 15’) from this protrusion to the top of the wall, one may lean a ladder in front of the protrusion, which enables the residents to make a single eiruv. However, if one leans the ladder to the side of the protrusion, it does not reduce the height of the wall. If the wall is 19 handbreadths tall (about 57”), such a protrusion is enough to enable the residents to make a single eiruv because there are fewer than ten handbreadths from the ground to the protrusion, and then fewer than ten handbreadths from the protrusion to the top of the wall. If the wall were 20 handbreadths tall (about 60”), two such protrusions would be needed to enable the residents to make a single eiruv; these protrusions may not be parallel to one another so that there will be fewer than ten handbreadths from the lower protrusion to the ground and fewer than ten handbreadths from the higher protrusion to the top of the wall.