Translation:Mishnah/Seder Moed/Tractate Sukkah/Chapter 1/8
Mishnah 8
One who makes a roof over his succah with spits or with the sides of a bed, it there is space between them as wide as the items themselves, [and he fills the gaps with materials eligible for s'chach,] the succah is valid. If one hollows out a haystack to make a succah for himself, it is not a valid succah.