A ﬂat head bolt with a bearing surface that is countersunk to a 150° angle. Although ﬂat, the head has a measurable side height causing it to protrude above its mating surface when it is completely tightened. Directly below the head is a square neck and a threaded section that has a uniﬁed thread pitch.
The square neck design keeps the bolt from turning as a nut is tightened. The ﬂat head feature gives a lower proﬁle on the front or top side of the fastening than a round head carriage bolt. Designed speciﬁcally, but not exclusively, for the garage door industry.