comments:
ambivalent0remark posted on r/parentsnark31w
We had a similar problem at our townhouse too. I screwed in some plywood to the wall (at the stud) at the thickness of the molding to even out where the mounts would go, then screwed the mounts into the plywood. It was ugly (though if you have the time/energy/tools it’d be possible to make it look nice) but it functioned safely. This is the model we used: https://www.walmart.com/ip/Evenflo-Walk-Thru-Top-of-Stairs-Baby-Gate-Natural-Wood/47623799