A sheet material conveying apparatus has at least one pocket running along a track, the pocket including a base section for receiving sheet material and an upper section including at least one upper gripper for holding an edge of the sheet material. The at least one upper gripper is movable between a gripping position and a non-gripping position, and the upper section is movable with respect to the base section to alter a distance of the at least one upper gripper with respect to the base section.