The slots are for the insertion of a cotter pin to secure the nut when used with a drilled shank fastener

F436 flat washers are manufactured from carbon steel to meet or exceed ASTM F436

1/4-20 x 2 1/4 Acorn Sleeve Anchor Zinc Plated (100)

7/8-9 x 5 1/2 Grade 5 Hex Cap Screw Zinc Plated

7/8-14 x 5 Grade 8 Hex Cap Screw Yellow Zinc Plated

1 1/4 x 6 Reduced Shank Drill Bit (1/2 Shank) Tie Wire Split Drive Anchors Zinc Plated The slots are for the1 1 4 x 6 Reduced Shank Drill Bit (1 2 Shank) . Expands the size range capacity of a 1 2 inch portable drill chuck. Common flute and overall length for minimal adjustment during tool changes. Precision ground for high degree of concentricity between shank and body diameter. Ideal for drilling in low and medium tensile strength materials.