Abstract: A sheet member (30) is positioned on the slats (18) of a reciprocating slat conveyor in a container (10). A strap (32) leads from the forward end of the sheet member (30) to and through a guide eye (38) that is mounted at an elevated position (26) adjacent the front wall (16) of the container (10). The strap extends downwardly from the guide eye (38) to a winding reel (36) driven by a motor (34). A block (40) is connected to the strap (32) in a position so that when the front end of the sheet member (30) has been moved by the strap (32) into an elevated position adjacent the front wall (16), the block (40) on the strap (32) will move through the throat (124, 108) of the guide eye (38) to the opposite side of a latch spring (42) that defines one side of the throat (124, 108). When in this position, the block (40) contacts the latch spring (42) and is hard against a reverse movement of the strap (32) and block (40) through the guide eye (38).