I would agree it is Saiphos equalis as the dark dorsolateral line is wide and the entire side is dark, while it does nor have strong dorsal markings, which contrast with the Eastern Three-toed Skink, Hemiergis talbingoensis. Both have an orange or yellow belly but Saiphos has black under the end of the tail.
For the technically minded, both have a moveable lower eye-lid but that of H. talbingoensis has a transparent disc while Saiphos does not.
These guys shelter in moist areas under rocks or logs in nature or whatever in a yard and spend much of the time cruising through the leaf litter hunting. that is why you would not see see them normally. The fact they are surviving in your garden is a very healthy sign that you are not into using heavy duty chemicals, especially pesticides, and have a healthy layer of organic mulch.
Blue