Ohalos 11:2

Regarding a portico that has cracked into two parts, if there’s impurity on one side, utensils on the other side remain clean. If a person placed his foot or a reed over the crack, he has combined the impurity. If he put the reed on the ground, it doesn’t convey impurity until it’s a handbreadth opening off the ground.

Ohalos 11:3

A thick wool coat and a thick wood block don’t convey impurity until they’re a handbreadth opening from the ground. Folded garments one above the other do not convey impurity until the topmost is a handbreadth opening from the ground. If a person is placed lying under the crack in the portico, Beis Shammai say that he doesn’t convey impurity but Beis Hillel say that a person is hollow and his topmost side conveys impurity.