A removable assembly adapted to be inserted into a shell defining a pair of grooves includes a support tray, a panel perpendicular to the support tray and defining a pair of gaps and a pair of handle assemblies. Each of the handle assemblies includes a trigger, a shiftable plate and a spring. The trigger pivots to the support tray. The shiftable plate engages with the trigger to rotate together with the trigger or disengage from the trigger under an external force to keep the support tray immovable during rotating the trigger. The shiftable plate includes an urging portion used to urge an outer surface of the shell to move the support tray out from the shell. The spring is urged between the panel and the shiftable plate to ensure the shiftable plate engage with the trigger.