On the left, the two halves of the plastic RBT mount. The RBT mount is designed for projection-accurate alignment of the film chips by use of registration pins that are can be moved sideways for horizontal position, and for vertical position in four steps of 0.1mm.
On the right is an open "fold-over" cardboard
One side of an RBT mount, showing the white adjustable
registration pins at the top of the apertures.
The RBT mount can be use to align the film chips
before taping them into the cardboard mount. To do this the RBT mount needs
to be modified by cutting away one edge as shown on the left. The photo
shows that the apertures are left intact by this modification. Also the
pins for mating with the other half of the RBT mount are removed to make
the inner surface flat.
The RBT mount is now ready for use as an alignment tool, so that the film chips can be accurately taped into position in the cardboard mount. A light box, and a straight-edge fixed to the surface of the light box (eg: double sided adhesive tape) are other useful items to make the job easier.
More information: Using the RBT mount as an aligment tool.