There are generally two types of rods for a card index:<br /> - plain rod with round hole that typically needs to be removed to insert cards. These are useful for safety (and not dumping cards out) or losing them (esp. in public settings like a library. - flat rod (various forms) allows cards to be 'locked" or released easily for filing efficiency, especially valuable for business use. - no rod at all; by 1911 there were more easily moved follower blocks which helped to get rid of the necessity of rods at all, at least in Byles' estimation.

Features include: - follow block (to bunch cards to the front of the drawer and hold them upright without falling over - bail stop - a mechanism to keep the drawer from being accidentally pulled completely out of the case.