Rangers had almost taken the lead on 19 minutes when Tom Tonks’ corner found Jake Charles who headed onto the crossbar.
The Boro were starting to get hold of the tie and United escaped a goalmouth scramble as the ball deflected around the box.
After showing his warning signs earlier in the game United skipper Paul Ennis rattled the Rangers’ crossbar on 32 minutes direct from a free-kick.
Straight on the break the Boro broke and Joe Cuff saw his effort from outside the box flash wide of the post.
FC United showed their warning signs during the first half and struck with two quick goals after the break both coming from Waddecar.
Rangers tried to muster a response with their best effort coming from Cuff with a low shot which was saved by Dan Lavercombe