Exodus 25:14

25:14 and put the poles into the rings at the sides of the ark in order to carry the ark with them.

Exodus 27:7

27:7 The poles are to be put into the rings so that the poles will be on two sides of the altar when carrying it.

Exodus 38:7

38:7 He put the poles into the rings on the sides of the altar, with which to carry it. He made the altar hollow, out of boards.