The roustabout was working on the catwalk attaching the wire rope sling to the Top-drive from the blocks. The Floor man on the rig floor lowered the wire rope slings down the v-door and onto the catwalk. The roustabout proceeded to attach the wire rope sling but wasn’t aware that it was twisted (and had stored energy), so he pulled the wire rope sling, as he did this the sling unwound and struck his hand fracturing a bone.