742. The Dimensions of an Alley's Entrance

Shabbos 17:14

In order for a pole or a beam to be sufficient to enable carrying in an alley, the alley’s entrance may not be less than ten handbreadths high (30”) nor more than twenty cubits high (30’). The width may not exceed ten cubits (15’). This is when the entrance does not have the shape of a door entry frame. If the entrance has the shape of a door frame, then one may carry within the alley even if the entrance is higher than 100 cubits, lower than ten handbreadths, or wider than 100 cubits.

Shabbos 17:15

If the beam over an alley’s entrance is decorated, which makes everybody look at it, it is valid even if it is higher than 20 cubits. The purpose of the beam is to distinguish the entrance. Normally, a beam higher than 20 cubits is invalid because it will go unnoticed. In the case of a decorated beam, however, since it catches people’s attention, it serves its purpose even when it is higher than 20 cubits.