Film

Pictures below are drawn for easy to get the shape of film entirely.
The film consists of four parts A, B, C and D. They correspond to labels of faces of tetrahedron T. Part A is supposed to include a point at infinity

so that it is omitted from drawing.

Look at Fig. 1.

: Complete film except part A. Lines PQ and SR are to be placed partitions.

: Skeleton of the film. The side view and front view are the same.

: Figure-8 knot. Comparing film with this, as you recognize, film is hollowed a bit around the center for easy to see.

: Film part D is twisted roughly 90

, that is not turning over.

Fig. 2 shows when one of parts is removed.

Back