Straighten up a gate that is "sagging"? Possible? Suitable?

[john68]

Built these two gates about 15 years ago, and they've worked reasonably well. Tried to make them form-strong by routing 50/50, etc., but I've noticed they've sagged in recent years.

I'm considering if it's possible to take them down and force them back into shape? And how would I do that, and preferably make it stay that way?

 

[Kalle B]

A diagonal brace that runs all the way would help a lot, but it doesn't look nice.

 

[Luc Reiner]

Have seen some gates with their own small discreet wheel that supports if it can work.

 

[z_bumbi]

Straighten them up and fit angle brackets in the corners, the ones that look like a try square. It might not just be about pressing back; you may have to possibly open some joints and adjust a little.