Be able to extrude aprons up for kerbs

Allowing the ability to raise an apron from the top and give it height would
allow such things as parking and kerbing rather than using concrete models.
Basically the idea is similar to Blender where you can extrude up the top
surface and the walls follow. The picture shows two aprons (grey and a white
one). Being able to ‘lift’ them would offer instant kerbing. The use of aprons
allow much more refined shapes than having to make and fit models