The Valve Stem Multi-Tool performs 4 separate functions:

1.  It tightens or removes valve stem cores. The T-handle portion has one end that fits over the valve stem and works as a valve stem wrench

2.  It deflates tire when screwed onto the valve stem. The T-handle portion has another end that will deflate the tire when screws onto the valve stem

3.  It fishes tubed tire valve stems back through the hole in the rim. Just slip the long end through the hole in the rim, thread it onto the end of the valve stem, and pull the tube into place. 
Note:  check the size of the hole in your rim - it must be at least 7/16" diameter for the head of the tool to fit through the hole.

4.  It seats valve stems on tubeless tire. Slip the long end through the rim, thread on a new tubeless valve stem, and pull the stem through the rim to seat the stem.  Use some BeadGoop on the stem to help it slip into place.

This is one of the handiest tire tools we own!  It's the same tool that comes with every BeadBrakR.