Dar
I got the impression he was refering to a verticle bar in the exhaust port to attach an exhaust baffle like the old Supertigre, K&B and McCoy engines used to use for a better idle before mufflers. The Silverline and Black Head Webras had bolt on mufflers along with baffle top pistons. The speed series used strap on mufflers until they changed to bolt on mufflers. ABC and ABC type engines do not have ports with bridges in them as there is no ring to catch in the ports, but ringed engines do.