Not quite a guitar but the owner was unhappy with the action on this Ukulele.  The slots in the nut are very shallow giving it a very action at the first fret and so making it very difficult to play barre chords at the top of the neck.

Quite a simple job. I took the picture after I cut the slot for the G-string to give an idea as to how much the action height can be reduced by.

A comment from the owner:

“Brilliant! much easier to use now. Thanks”