5/16"-18 x 2 T-40 Flat Head Self Tapping Trailer Deck Screws, 100 Pack | Star drive (six lobe) floorboard screws fasten wood decking to steel trailer and truck bed frames. Type F, phosphate.

TYPE F SELF-TAPPING POINT - cuts machine threads directly into steel crossmembers up to 1/4" thick; drill a pilot hole, drive with an impact, no nut and no pre-tapping

FLUSH COUNTERSUNK FLAT HEAD - nibs under the head cut a clean countersink in hardwood and softwood decking, so nothing catches a boot, a strap or a skid

STAR DRIVE, NO CAM-OUT - deep six-lobe recess takes full impact-driver torque without stripping; far more re-drives than any Phillips deck screw survives

REMOVABLE, SERVICEABLE JOINT - machine threads in the steel survive board replacement; back the screw out, drop a new board, drive the same screw home

SPECS (5/16"-18 x 2") - T-40 star drive, pilot per the Type F hole chart (see product images); suits 1-1/2" boards over steel frames; steel Type F thread cutting screws, made for trailer deck and floorboard replacement