This photo shows what is under the front end of the pelvic cushion. The "1" arrow indicates the pin that is pivoted into the clevis (the "2" arrow) when the cushion is locked in at the horizontal position. The black metal handle would be pointing straight down when locked.
If the assembly separates then the pin can rotate out of the front end of the clevis. The other instruction sheet ("CROSSBAR") attached explains how to make sure the assembly is drawn together tightly.
