Abstract: An apparatus is provided for locking rack-mounted electronic devices within a rack upon removal of one of the electronic devices from the rack. The apparatus includes a shaft rotatably connected to the rack and provided at each slot position with a set of paddles, including a locking paddle and a trigger paddle. With the rack populated with devices, the removal of one device from a slot causes a block attached to the device to urge against a trigger paddle, which rotates the shaft. As the shaft continues to rotate, with the motion of the block caused by the removal of the device, the locking paddle for each slot is rotated into a position such that an attempt to remove any of the other devices from the rack causes the associated block to abut the locking paddle, which does not yield.