I'm impressed, and scared by your dogs
Justifiably so, Chardonnay! I've spoken to other Lakeland terrier owners, and door-opening skills seem to be a speciality of the breed.
The friend who looked after Houdini dog was quite convinced he could walk through walls. The first night he stayed at hers, he was in the utility room with her dogs.
Less than an hour later, he'd managed to remove a board that was hanging on hooks (to stop her dogs from scratching the paintwork) open the utility room door, open the kitchen door, jump or clamber over a baby gate, go upstairs, open her bedroom door and join her and her DH in bed.
All the doors had round door knobs, and 2 of them opened inwards.
We also went out for the evening and came back to find all 4 dogs sitting in her front garden when we got back. I'm convinced that someone tried to get in via the garden, ran off when the dogs came out of the dog flap, and left the side gate open. DFriend thinks that Houdini dog taught them to form a canine pyramid so he could undo the bolt at the top of the gate and let them all out.
He was the cleverest dog I've ever known.