Think of the vacuum jug, we were talking about earlier. The internal flask has to be closed by an internal lid: The internal roof. It consists of 12 triangles made of 2 layers bent plywood. It is attached to wood laths, which are skrewed on the top of the internal wall. They are quite heavy, so we had a machine to lift them on the first floor. But putting them on place was manual work. Several strong men and women were needed.

All the 12 triangles are ready to be raised.

A kind of "banner" got raised in the center of the 1. floor to maintain the triangles in position.

To each triangle a wood lath is attached to make handling easier

When the triangles are first placed, their junction has to be cut exactly and tight.

One of the triangles is pulled in position.

Several galvanized steelmounts are skrewed on the junction of 2 triangles to maintain them in position

Work has to be examined.