Scratch

you could do this

add this script to the wall

when green flag clicked
set (variable) to one
forever start
if touching (the sprite you want it to be solid to)
set (variable) to one
if end
if not touching (the sprite you want it to be solid to)
set (variable) to zero
forever end

You may be asking: How does this help? well here's how

put this script under the sprite you want it to be solid too

when green flag clicked
forever start
if key right pressed start
change x by (amount)
if (variable) equals one
change x by -(amount that you put above)
both ifs end
forever end

Hope this helps.

:0