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

1-8 x 8 1/2 Socket Cap Screw Alloy

#12 Heavy Duty Jobber Drill Bit

1 1/2 x 8 Ship Auger Wood Bit

5/8-11 x 6 Hex Sleeve Anchor Zinc Plated (10)

8 x 1 1/4 Phillips Wafer Hi-Low Cement Board Screws w/ Nibs Sharp Point Ruspert Coated - Carton (5000) 10-24 Socket Cap Screws Alloy The slots are for the8 x 1 1 4 Phillips Wafer Hi Low Cement Board Screws w Nibs Sharp Point Ruspert Coated Carton (5000) . Meets F. I. P. 1000. 7 for torsional strength and drill speed Ceramic coating provides protection from corrosion Nibs under head clamp board firmly