The Altar of Burnt-Offering: Furnished with Rings and Staves
Source: TTT
Exodus 27:6, 7
Additionally, make poles of acacia wood for the altar and overlay them with bronze. / The poles are to be inserted into the rings so that the poles are on two sides of the altar when it is carried.
Exodus 38:5–7
At the four corners of the bronze grate he cast four rings as holders for the poles. / And he made the poles of acacia wood and overlaid them with bronze. / Then he inserted the poles into the rings on the sides of the altar for carrying it. He made the altar with boards so that it was hollow.