Some crucifixes have a block under Jesus’ feet, and others do not. What purpose did that block serve?
It is called a suppedaneum and cruelly enabled the person crucified to straighten his or her legs, thus prolonging death by asphyxiation.
For this reason, we read in John 19:31-33 that Pilate sent soldiers to break the legs of Jesus and the two criminals crucified with him so they could be buried before the Sabbath began. Because Jesus had already died, they did not break his legs.