Quad Rail

The term “quad-rail” typically refers to AR-style rifle handguards that have Picatinny rail sections built into them. These rail sections tend to run the entire length of the handguard and are placed at the top, right, left, and bottom of the handguard—four rails in all. Quad-rail handguards have become less popular in recent years, particularly with the rapid adoption of the M-LOK attachment system which allows for a more streamlined profile, unobstructed grip surface, and are lighter. Sometimes quad rails are colloquially called “cheese graters” for their sharp angular Picatinny rail sections that can be uncomfortable to hold with bare hands.