We used to have a nice handle and lever style latch on our backyard gate. It was very attractive, and allowed operation from both sides. The problem was that it turns out it wasn't dog proof. Our new dog, Luna, was able to "bonk" into the gate and get it to flip open. She escaped into the world a couple of times, only to have neighbors return her. That's rather embarrassing, so that gate latch had to go.
Everyone has seen the standard kind of gate latch. It consists of a horizontal bar that attaches to the door (if it's inward-swing), and a metal bracket with a slot for the bar to fit into and a hinged metal piece that goes up and down to lock the bar in. It's serviceable, and (at least in our case) dog-proof. The difficulty is that it has no provision for operation from the outside.
Well, not quite. There is a small hole in a tab on the latch that you're supposed to tie to a piece of string run through a hole in the fence. We've all seen those, and the various failure modes.
If the string in any way restricts the free movement of the latch, the whole mechanism is bound to fail. And, of course, in this case, the failure mode is unlatched, dog-roaming mode. Even if the string works, it won't work for long - the wood fence material will no doubt shred the string before too long.
Well, you could attach a wire instead of the string. The problem there is that a solid wire is even more likely to impede the free movement of the latch.
No, what you need is a frictionless, low profile linkage between the cable and the latch.
What you need, is a fairly standard part from the RC model hobby industry: A clevis linkage. A clevis linkage is a small pair of long, thin metal plates that normally sit parallel to each other. At one end of each, there is a round grommet through which you run the cable and either crimp or solder to permanently attach the linkage to the cable. At the other end of one of the parallel plates is a pin, and at the end of the other plate is a hole inside which the pin sits.
Solder a foot long (or so) piece of 1/16" braided cable in the clevis, and use a crimp coupling to form a finger loop at the other end. Drill a 1/4" hole right behind the top of the latch. Run the clevis coupling end of the cable through the hole and attach the clevis pin to the latch.
I have to admit, I didn't come up with this idea myself. We used to have this same problem on our other gate - the string wore out almost immediately, and I was just used to reaching over the fence (I am tall enough) and flipping the latch by hand, but that didn't help Scarlet. So one day while I was in our local hardware store, they had a display for a gate latch improvement kit. It was virtually identical to what I've described above, except that their kit also included a very, very large spring intended to go between the gate and the latch to help insure closure, and a washer with a flange that was meant to sit in the hole and hold the base of the spring centered around the cable hole.
I'd heartily endorse that kit, except that the local hardware store doesn't carry that product anymore, and nobody else has ever heard of it.
The other problem is that while that kit worked flawlessly on the gate where I installed it, a quick test shows that it wouldn't have worked quite so well on this gate. The issue here is that the latch is installed on a 2x4, but the hole you drill for the cable is above that 2x4. That means that the washer / spring base would sit a good two inches behind where it's designed to. I'd either have had to build up the face of the fence at that spot so that the hole emerged "at grade" or modified the kit's spring somehow. But that implies I would have had the kit to start with - I didn't.
Instead, it appears that, at least in this case, the spring is unnecessary. Of course, YMMV.