Ohalos 8:3

The following things convey impurity but don’t block it: a chest, a box, a cupboard, a beehive of straw or of reeds, and the reservoir of an Alexandrian ship, when these things don’t have bottoms or can’t hold 40 forty seah of liquid/two kor dry (about 140 gallons); a curtain, a leather apron, a leather bedspread, a sheet, a mat and matting when these things are not made into tents; a domesticated or wild animal that died, and foods that are susceptible to ritual impurity. Also, a hand-powered mill.

Ohalos 8:4

The following block impurity but don’t convey it: a web of warp threads on a loom, the ropes of a bed, mesh baskets, and window screens.