Square Head Set Screws
Square head set screws have a cup point allowing them to dig into the surface for a firm hold.  The square head style allows for tightening with a wrench for when more torque is needed. 
Unit of Measure
Items
Sqaure Head Set Screw

1/4-20 x 3/8 Square Head Set Screw Half Dog Point (100 Per Box)
Price $59.12

Sqaure Head Set Screw

1/4-20 x 1/2 Square Head Set Screw Half Dog Point (100 Per Box)
Price $59.12

Sqaure Head Set Screw

1/4-20 x 5/8 Square Head Set Screw Half Dog Point (100 Per Box)
Price $61.00

Sqaure Head Set Screw

1/4-20 x 3/4 Square Head Set Screw Half Dog Point (100 Per Box)
Price $61.28

Sqaure Head Set Screw

1/4-20 x 7/8 Square Head Set Screw Half Dog Point (100 Per Box)
Price $61.48
Size N/A 1/4"-20
Length N/A 3/8" N/A 1/2" N/A 5/8" N/A 3/4" N/A 7/8"
Type N/A Half Dog Point
Material N/A Alloy Steel