Playbooks

Mtn Y Corner is a trips-based play-action style dropback concept out of Shotgun Y Off Trips Nasty that uses pre-snap motion to shift the trips receivers before the snap. The backside X runs a deep corner route stemming from the outside, the boundary TE releases vertical then breaks outward on a corner of his own, and the inside trips receivers work an out and drag underneath while the fullback/H-back checks down on a shallow crossing route. This is primarily a man beater with high-low corner routes on the same side designed to stress a single defender in man coverage, with the underneath drag and out serving as zone beater checkdowns if the deep shots are covered. The primary read progression starts with the outside corner route, moves to the TE corner working the same third of the field, and finishes with the underneath drag or check release if both corners are blanketed.
Pre-snap, check the safety alignment: a single high safety means this play has a strong chance to hit the corner route for an explosive gain. Watch cornerback press versus soft alignment on the trips side, since press man leaves the corner routes vulnerable to a well timed throw. Post-snap, key any user-controlled defender dropping into the deep third or shading toward the trips corner routes, as a lurking safety can jump the throwing lane. Look for zone drops from linebackers underneath, since a sinking Cover 3 zone can undercut both corner routes and force the quarterback to the drag route. Beware disguised Cover 2 shells that roll a safety over the top late, which can turn a big play read into a costly interception if the quarterback locks onto the first corner route.
Use the pre-snap motion to identify if the defense shifts a linebacker or DB, which tells you whether you are facing man or zone before the snap.
Attack single high safety looks (Cover 1 or Cover 3) since the double corner concept overloads one side of the field against a lone deep defender.
If you see two safeties deep (Cover 2 or Cover 4), hot route the outside corner route into a hitch or comeback to prevent bracket coverage from taking away both verticals.
Pair this play with Mtn Curls Y-Wheel or Mtn Y Pivot in the same set to keep defenders guessing between deep shots and quick underneath answers off similar formation looks.
Best called on second and long or third and medium when you need a explosive gain but still have the drag route as a checkdown safety valve against pressure.