Playbooks

Mtn FL Screen is a wide receiver screen out of Shotgun Spread Y-Flex that uses two vertical clear-out routes to pull coverage away from the boundary. The two outside receivers to the top of the diagram run a vertical seam and a wheel-style go route to occupy deep defenders, while the flanker runs a screen route back across the field to the opposite sideline as blockers set up in front of him. This is a zone beater designed to attack defenders who bite on the vertical stems, and the primary read is the bubble/flanker screen first, working through blockers as they release downfield.
If you are on defense, key the flanker at the snap instead of following the two vertical routes, since screens are designed to punish defenders who chase the deep clear-outs. Watch for a user-controlled defender sitting flat in the short zone to the flanker's side, this lurk assignment can jump the screen route before it develops. Cover 2 and Cover 3 zone shells with linebackers who drop deep instead of reading the backfield are the most vulnerable to this concept. Man coverage with press corners can shut this down quickly since the screen has nowhere to go if the blockers get beat off the line immediately. Blitz packages that send extra rushers up the middle can actually help the offense here, since fewer defenders remain to read the screen develop to the flank.
Call this play against zone shells like Cover 3 or Cover 4 where linebackers and corners will widen their eyes on the two vertical clear-out routes and lose sight of the screen developing behind them.
Use pre-snap motion if available to identify man versus zone: if the defender assigned to the flanker follows across the formation, expect man coverage and consider checking to a different play at the line.
Let your blockers get out in front before throwing the screen, patience is key since throwing too early into a crowd of defenders results in a loss.
Pair this with Mtn HB Cross Screen or RPO Alert Screen in the same set so the defense has to respect multiple screen concepts and cannot key on receiver alignment.
Best used on early downs (1st or 2nd) when defenses are more likely to sit in base zone looks, and avoid calling it against aggressive man blitz packages that bring extra defenders off the edge.