Hi guys just about to take a mould of my roof the only bit that concerns me is near the door, as in the picture will the mould lock in this little bit? 

Mechanical lock. Yes we’ve all had those.

In the 70's I was Project Engineer in charge the design of the inspection media for the T68 ( no it was an Australian Land Train not a Russian tank). Only had problems with one fixture. I worked out we could spring the panel out of the fixture so we wouldn’t need to go to the cost of a two part fixture. Well you could spring the panel, but you can’t spring a wooden buck. Whoops.