"Remove footprint" equivalent for wall objects? [SOLVED]

Why do I often find a solution right after I post, even though I've spent a lot of time before trying to solve the issue? Does this step unlock something in my brain??

Here is what I did:

1) Since posters can overlap with other wall items, I've cloned a poster in S4S, and took a look at the wharehouse. First I've seen that there wasn't a 'Footprint' section. Then I went to Object Definition > Footprint and found this :



2) As a test, I opened my string light package, removed the footprint section, went to Object Definition > Footprint (for each swatches) and copy pasted the same numbers as the ones of the poster.

It worked!