Stone walls, similar to wooden fences are supposed to be 1.5 blocks high therefore preventing almost anything from jumping over them. I have built shops and made the counter out of stone walls to prevent the shopkeeper from leaving his position. I've used command blocks to spawn villagers with specific trades and set them behind counters yet the next day I find the villagers running around my village.. Heck I even added a half slab underneath them and another above them but still they escape.. "Grrrrr"

This is completely ruining the adventure map I'm creating for my children to play on.. It's really frustrating especially when I have to restart with another command block and heaps of code pasted in to re-summon the shopkeepers back into the right place.