From what I was told in one of my questions is for your chickens safety 1/2 is what you want to use.
The areas I needed to cover were just windows, vents and I made a screen door last week and used 1/2" hardware cloth.
When I did have to join my chicken wire together, I had smaller size zip ties and lashing wire laying around form doing cable and fiber work years ago. The wire was a stainless steel and I just cut short lengths and twisted them tight to seal the joint.
That is if it wasn't a place where I couldn't use a 2 by to secure the joint, like 3baymares said. My feeling is the best when it can be used.
Oh, and as weird as it sounds, I looked it up and a younger mouse can fit through a 1/2" opening. I didn't believe it but it's on the internet so it must be true!!!