Pocket signature feeding machines have been provided with a double indicia scale on a pocket backplate and the scale is related to the centerline of the pocket so that the signatures may be precisely centered in the pocket when the left and right signature guides have their respective indicators pointing to the same indicia on the pocket backplate scale. A sheet that is 10 inches in width can be centered by having the respective left and right indicators set at a number 10 on each scale portion of the double scale. The signatures are bowed by side guides engaging opposite vertical edges of the signatures in the hopper. Also, an outer scale with indicia thereon is provided for setting the side guides at a distance that will cause an automatic, correct bowing of signatures. A gripper mechanism cooperating with a signature picker times the drop of signatures onto the saddle of the gathering conveyor. Indicia associated with the gripper mechanism allows a quick positioning of the gripper to a previously used position for the same size signatures previously run so that the new signature drop will be substantially the same as the signature drop for a previous run.