An aspect of some embodiments of the current application is a doorstop to a drug delivery apparatus that encourages a user of the apparatus to perform the proper usage steps in the proper order. For example, a user may be expected to receive an injector in a transport state, open it to an open state, insert a cartridge, and/or close the cartridge before operation. The doorstop may have an obstructing mode, optionally preventing closing of the door. The cartridge may optionally have a non-obstructing mode allowing closing of the door. Inserting the cartridge may optionally cause a doorstop to move from the obstructing mode to the non-obstructing mode. In the non-obstructing mode the doorstop may optionally prevent removal of the cartridge.