How to remove an object's footprint

Hi! I'm trying to make a mural that doesn't have a footprint... or maybe it's a more like wall print? The mural has several swatches, some of which are narrower, and I wanted to avoid having to use MOO to place it.

I followed this tutorial and now I can't place the object, I get a message saying the object must be placed against the wall, but it hovers half a tile away.

Help very much appreciated