In addition to what jncranton wrote, the plate with the rail is a perfect fit for sliding in the brick with groove:

You can see an example of that technique in the Cloud City set:

In addition to what jncranton wrote, the plate with the rail is a perfect fit for sliding in the brick with groove:

You can see an example of that technique in the Cloud City set:

In addition to what jncranton wrote, the plate with the rail is a perfect fit for sliding in the brick with groove:

You can see an example of that technique in the Cloud City set: http://belay.peeron.com/scans/10123-1/32/

In addition to what jncranton wrote, the plate with the rail is a perfect fit for sliding in the brick with groove:

You can see an example of that technique in the Cloud City set: