A housing includes a wall, a connector, a coupler, and a foot pad. The housing includes a bottom surface, a recess defined in the bottom surface, and a discontinuous ring-shaped engagement member surrounding the recess. The engagement member has a first gap and a second gap aligned with the first gap. The connector is connected to the engagement member and is rotatably engaged in the first gap. The coupler includes a main body and an engagement portion extending from a circumference surface thereof. A first engagement hole defined in a central portion of the main body. The main body is rotatably connected to the connector and engagable in the recess. The engagement portion engages in the second gap. The foot pad is connected to the coupler to seal the first engagement hole and received in the recess.