How does it relate to the tree shape?
Scroll down to the Sentry and there is a description, indicated for narrow bodied types:
Funny you should reference that page because I tried a Sentry today and looked it up and saw that page and then wondered what j-bar meant. I was hoping to find a picture of a bare tree so I could get an idea, or have a more descriptive explanation of how it is different from other trees vs. “designed for mules and narrow-bodies animals.”
I just requested a pic from Crest Ridge. I’ve never heard of it! Gotta see…
Pocket Pony, here is an interesting site about western saddle trees