Originally I did these moulds as a solution for the window sills ledges.
Which originally had wood ledges. This proved to a be super easy solution.
I made 17 different variations of window moulds differing in lengths and orientation plus duplicates so we did could let them cure and work on other windows we probably had 200+- windows.
The largest mould was 9 feet long picture window in the lobby.
End result was durable and beautiful, no termites will munch on these!
The moulds where fastened to the brick anchors etc,
lots of mould release vaseline worked and was cheaper.
Most important! sealed openings with plumbers putty.
I did some research on the best cement blend ended up with;
1 part cement
2 parts sand
2 parts gravel
we also added chopped fiberglass don't remember amount
and a wire mesh frame
I used a modified angle grinder with an offset counter balance as a vibrator
to make sure cement filled all voids
I did my homework B-)



On this window sill casting I cemented a marble slab on top to create a ledge below the mailboxes

Looks nice!


Base of steel columns got the mould treatment also.