Nylon Bridge Rest Heads can be fitted to any old Cues or a manufactured Cue Rest Stick. Or you can make your own custom Cue Rest Stick to suit.
They are easy to attach by pushing on to any blank Rest Shaft
The Bridge is effectively a tall Rest.
Where a Rest is required and the Cue Ball is on just the other side of another Ball, a Cross Rest will not do the job because the Cue needs to go over the intervening Ball
Such shots are only possible with a Bridge
A Bridge will be required fairly regularly on a large Table and occasionally on smaller Tables. So ideally the minimum for any Table is both a Cross Rest and a Bridge Rest