Sure thing, partner. Let’s keep it simple: a metal bar that slides in a slot on the gate, a small latch that only a hand can pull—no bolt that’ll jam on a dog’s paw. Use a quick‑release pin so you can open it when you need to, but it stays locked when the gate’s closed. Build the bar from sheet steel, drill a hole, bolt it to the gate frame, and attach a cheap brass latch with a pull string. Easy to make, tough enough for a terrier, and you won’t have to wrestle a lock every time. Ready to get the tools?