That is the idea Bob, nothing inside the spider gears can turn, so the differential function is "locked".
It becomes a straight reduction gear unit and both axle shafts turn at the exact same speed.
You can only do it if you have free wheeling hubs for when you are on the hard surfaces.
Very hard on the drive train when you turn a corner - one tyre has to skid or something breaks, but very effective in mud, or when you have 1 wheel off the ground.
PK