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

1 1/4-7 x 11 Socket Cap Screw Alloy

17/32 x 6 Reduced Shank Drill Bit (1/2 Shank)

#46 Heavy Duty Drill Bit - Stubby Length

1/2-13 x 8 Grade 8 Hex Cap Screw Yellow Zinc Plated

7 x 2 1/4 Simpson Trim-Head Wood Decking Screws - Square Drive 305 SS White 02 - Deck Pack (350) Phillips Flat Machine Screws Type F Zinc Plated The slots are for the7 x 2 1 4 Simpson Trim Head Wood Decking Screws Square Drive 305 SS White 02 Deck Pack (350) Durable, powder coated finish painted heads blend with decking material 0. 230" diameter #1 square drive, trim head Type 17 point for fast starts Coarse threads approximately 2 3 up the shank draw the decking tightly to the substrate Slender #7 shank for finish work and trim Pre drilling recommended near board ends to prevent splitting Use with stable woods