To provide a combination body of a novel end cap and an installing support.

A combination body of an end cap and an installing support has an end cap 11 engageable with a support bracket 3 in an engageable releasable state, one of the end cap 11 and the support bracket 3 has a groove hole 20 opening in the lateral direction for housing a projection 21 extending in the other shaft direction of the end cap 11 and the support bracket 3 and a closing means for preventing the projection from escaping from the groove hole 20 opening in the lateral direction, the closing means has a rotatable locking collar 19 surrounding the groove hole 20 opening in the lateral direction and having a circumferential directional inlet opening, and the circumferential directional inlet opening can be adjusted to the groove hole 20 opening in the lateral direction by rotating the locking collar to an opening position from a closing position on the groove hole 20 opening in the lateral direction to thereby selectively provide the approach to the groove hole 20 opening in the lateral direction through the circumferential directional inlet opening.