How the part fits? A 48" tension bar is actually 46" in length. It is designed to fit through the last weave of the chain link fabric at the point of termination.
Where is it installed? A tension bar is installed at every point where you terminate your chain link fence.
How many do you need? You will need (1) 48" tension bar at every corner, end, and gate post. For every stretch of fence, you will need (2) total.