This action would remove the current edge, and in its place it would make 3 edges; of which the middle one would be the same as the one that was removed; except that this new edge is created at the location of the architect. The other two edges that are created would be orthogonal to the central edge

//In short, this creates a rectangular shape, with one edge of the rectangle missing (which is where the first edge used to be) //

You can always locate the architect accurately using the headsup command line, before invoking this action.