A fitting includes a stem extending in an axial direction and having a threaded surface adapted to be screwed into an upright wall. An annular head portion is connected to the stem, and has an abutting surface wall proximate to the stem and extending in a transverse direction relative to the axial direction for abutting against the upright wall when the stem is fixed in the upright wall. A cylindrical anchored member extends from the head portion in the axial direction away from the stem, and has a distal end distal to the abutting surface wall. A holding member includes an anchoring portion which is elongated in the axial direction to be sleeved on and to cover the anchored member, and a holding portion which is formed integrally with the anchoring portion for holding a support member. A fastening member is disposed to fix the anchoring portion relative to the anchored member by tightening along a radial direction relative to the axial direction.