Zavim 4:2

Pursuant to the previous mishna, the loaf of trumah also remains clean if the zav banged against a main beam, a rafter frame, a water pipe, a shelf – even one that was attached by ropes, an oven, a mill receptacle, a lower millstone, the support of a handmill or the seah measure of an olive-grinder. Rabbi Yosi adds if he banged against the beam of the bathhouse attendant, it remains clean.

Zavim 4:3

If he banged against a door, its bolt, its lock, an oar, the hopper of a mill, a weak tree, the weak branch of a strong tree, an Egyptian ladder that isn’t secured with a nail, or a bridge, beam or door that isn’t affixed with clay, utensils or food that fall from them are rendered unclean. If he banged against a chest, a box or a cupboard, they are rendered unclean but Rabbi Nechemya and Rabbi Shimon rule them clean.