Here is another angle of the groove and where it starts from the down slot. Note the groove goes more than 3/4's of the way around and gets shallower towards the end. The groove coming down is very deep to allow the spring clip to rest below the suface level of the glass. This was done to allow the insulator to be inserted into the chair leg. The wire clip had a 90 degree bend that would click into place in a hole drilled in the side of the chair leg to hold the insulator in place.