For some reason it is suprisingly easy to forget that you need hex nuts if you are building with either carriage bolts or hex-head cap screws – I have done it often enough to know! Heavy-Duty Hex-Head Cap screws and carriage bolts are great for exterior projects, but you need to use the correct nut too. These heavy-duty nuts are the perfect match for our hot-dip galvanized fasteners. Mix or match for pricing discount. Imported.