Run fencing...

[Vikinglike]

Is galvanized 48” high fence, with 2” by 4” openings adequate for a chicken run?

 

[meetthebubus]

No
...research chicken runs you'll get lots of ideas

 

[Acre4Me]

It would keep them IN if you clipped their wings. It would be less effective to keep out most things. A 4’ fence can be jumped over by dogs and other canines. A chicken can fly onto or over that height. A rodent or similar small animal can easily move through the fencing.

Chicks would’ve able to go through those openings as well, so if you had chicks then they would need to have some kind of barrier up to keep them from walking right through. When chicks get old enough to fly well, they have light and trim bodies and the adventurous ones will fly up and over a 4’ fence, so a cover over The run would be helpful.

BUT, maybe you don’t have too many predators or have other means or fences up that keep out larger predators. So, if it’s what you have available it could work. Clip wings or cover the top to keep chickens IN and aerial predators out. Don’t leave food out as rodents will love it, and set up a colony.

Good luck.