Staffy doing a runner from the garden.

When i was looking to move a few years back my first priority was the garden for the dogs..lol..(never mind bedroom space for my sons etc.
My garden is perfect for my 3,with a few additions and following the dogs round before i first moved in to see their reactions and any escape roots.
I treat my garden like it was a for a toddler,looking from every angle,upstairs windows,you get my drift.
Ive a good quality fencing and chained up gate with locks,i dont ever leave my dogs out in garden as a form of exercise though as wouldnt you get bored and pi$$ of if nothing to do,i have springpole etc what i do with them and boomer ball etc but thats just extra stuff i do.Try not to let him out if he hasnt had a good run etc as boredom will take over and they will try escape.
If a male dont forget he can smell a bitch in season miles away,CATS are another reason,they have been with me in the past,water pistol soon solved that.
You could also make it a good place to be by adding things he enjoys and mix with him when out there,Good luck and hope you sort it.