Pulling a three-position lever located at the right side of the S100 receiver tang to its rearward position blocks
both sear and trigger movement, and it also blocks bolt rotation.
Similarly, position blocks
facing one another as shown in Diagram III-B.
Forward is Fire (revealing a small red dot indicator); the middle position is Safe, preventing the trigger from firing but allowing the shooter to work the bolt to unload the rifle safely; and the rearward position blocks
both the bolt and the trigger.
This closed position blocks
the body from coming through, forcing the right shoulder to come over the top in the downswing.
While students work in pairs, they are asked to position blocks
for each other in a way such that "the fewest number of faces can be seen," "about half of the number of faces can be been," and "the greatest number of faces can be seen" for different blocks.