[Talk-GB] How would tag or name this wall crossing?

[Michael Collinson]

What do you call the type of wall crossing the that consists of two 
stone pillars placed close to each other (usually in a drystone wall) to 
leave a gap wide enough for humans and sheep dogs to squeeze through but 
not cattle or fully-grown sheep? Has anyone one got a barrier= tag for 
them?  Just got back from Middlesmoor in Nidderdale where there are ton 
of them. They are typically not raised, so not a stile, and typically no 
gate, just a gap.

Mike