1/4"-20 x 3-1/2" Zinc Plated Grade 2 / A307 Steel Coarse Thread Square Head BoltsType: Square Head Bolts
Head Style: Square (3/8" Wrench)
Thread Size: 20 (Coarse)
Hardness: Grade 2 / A307
Type: Square Head Bolt
Box of 6.
A square head bolt has a four-sided head. Compared to standard hex bolts, square bolts have a greater surface in contact with the part being fastened, and therefore provide greater resistance to loosening (though also greater resistance to tightening). Square bolts are typically mated with square-headed nuts.