All three modules that will be part of the convention layout were put together in my train room in every possible configuration and thoroughly tested both for track and electrical. I am satisfied that these will work correctly.
As we will be setting this layout up at the 51 inch height, the 40 inch width of the roll of table cloth material we have been using as a skirt will be too short. So I have cut the roll into 25 48 inch lengths so we can use the longer length vertically and pin them to the bottom edge of the module frames.
Here the block is shown with the grooves up.
Here is the block how it is used with the grooves down over the rails while the modules are being clamped together from underneath.
This does seem to help get the track aligned between modules when I was setting up the modules by myself.
And I have been running all of my trains back and forth over the 3 modules which total about 11 feet in length. No derailments at all anywhere and I ran all of the trains I am bringing to the show.