An interlock system may control a sequence of installation of circuit board assemblies into a chassis and/or removal of the circuit board assemblies from the chassis. In one embodiment, an interlock member may inhibit installation of one circuit board assembly until another circuit board assembly has been fully installed in a chassis. An interlock member may also inhibit removal of the one circuit board assembly until another circuit board assembly has been removed. In some embodiments, an interlock member may inhibit use of injector/ejectors to inject or eject a circuit board.