Duster's Limp Theory

Duster was still training in Thief Arts when Wes introduced him to "Wall Staples". Wes showed Duster how to toss the staples into the wall, and to climb up and add more.
Duster gave it a shot. He, however, failed. He couldn't get the first staple in the wall.
"Duster, here's how it goes. Thrust it towards the wall and toss about 6 inches away from it." He took a staple for an example, but in his thrusting technique, he spun out of control and the staple sank into his leg.
And that's how it all happened.