What this tool is: the tool the books hope you never find. Enter your legs and the tease — it moves each line, computes the true win probability at the teased number from the margin model, prices the whole ticket against the payout, and hoists the WONG flag when a leg crosses both key numbers.
Enter each leg's CURRENT spread from that team's side: favorite laying 7.5 = -7.5, dog getting 2.5 = +2.5.
NFL margins spike on 3 (~9.5% of games) and 7 (~5.7%). A 6-point tease that CROSSES both — favorite -7.5 → -1.5, or dog +2.5 → +8.5 — swallows those spikes whole, historically pushing a leg's win rate past the 73.9% a two-team -120 teaser demands. Tease through dead numbers instead and you're paying parlay juice for coin flips dressed as locks. The tracks above show each leg's crossing; volt spans that swallow both pink pegs are the ones Stanford Wong wrote the book about.