Disclosed are removable “locking pins” that hold the front and rear housings of a wearable device together. These pins fit into receiving channels in the walls of the housings. Unlike screws or other fasteners, these pins do not take up space needed for internal components of the device. Unlike snaps, the pins are usable with housings that are very rigid (e.g., metal or ceramic). In some embodiments, the pins are entirely hidden from view, and thus they do not detract from the appearance of the device. Also in some embodiments, the pins fit entirely outside of a water seal for the device, thus reducing cost and assembly complexity.