In our models the window and door sills are generally constructed by rolling a window sill wrap around a template of card. The rolling technique is not unlike creating a very thin hand rolled cigarette. Our models usually show where to set a fold in each window sill wrap to allow the rolling to be achieved accurately.
When cutting out the thin and narrow window or door sill templates it is a good idea to coat the template after cutting with PVA glue and then letting it dry to prevent the card delaminating when being handled.
The idea of this construction technique is to wrap the card and leave a tail of the wrap that can be glued over the lower window or door cutout in a wall and also be glued down the interior face of the wall. It is a good idea to also glue the underside of the window or door sill at the front of the wall for extra strength.
Where one of our models uses window or door sills that are constructed differently then this will be fully explained in the model Assembly Instructions.