How to snap mesh object to the back of the footprint/grid?

I have a closet object that I edited to have a shorter back, but this means that there is a leftover grid behind it (so it won't fit flush against the wall). I have tried using the 'adjust footprint to fit mesh' button but this hasn't fixed it, and I have also tried removing the footprint but it still either goes through the wall and out the other side (i.e. intersects) or does not sit against the wall. I have read that it's possible to manually edit the footprint but I'm not sure if there is an easy way to do that or if there's a simple 'move to the back of grid' option (so the back of the closet would line up with the back of the grid?)