Electronic device assemblies may have multiple parts. A first electronic device assembly structure may be attached to a second electronic device assembly structure using a locking member. The locking member may include a tip portion that is inserted into a guiding channel in the assembly and a disposable portion that breaks away from the tip portion during assembly. Barbs on the locking member tip may resist retraction of the tip following assembly. A cam locking structure may help hold the first and second structures together. Locking features may resist longitudinal motion between the first and second structures. Snap features may provide a fail-safe mechanism to prevent disassembly of the assembly following an accidental dislodgement of the tip portion. The tip portion and assembly structures may be configured to resist bowing in the assembly structures.