Sideline

Predict on any live line

Take a view on somebody else's call: back it to hold, or back a rail to break. Both sides are priced in the open from the corridor's own survival probability.

Hold

Pays if the corridor keeps both rails to the very end. You are backing the author's read.

Breach

Pays if a rail gets touched before the end. One corridor, two sides, priced in the open.

The corridor you back keeps running whatever you do. Your ticket is separate from the author's and settles on the same outcome. As the price leans toward a rail the hold probability falls, so hold gets dearer and breach gets cheaper, live.