The brake itself is attached to the boom at the vang fitting. One side of the line is deadended at the toerail, the other goes through a block at the other toerail and back to a camcleat and winch for tightening the brake. You need to be able to get a lot of tension on the brake for it to work properly, and also to be able to release it quickly. And indeed it is handy to use to move the boom to one side at anchor so I can put up an awning-end boom sheeting has some drawbacks. :)