A -- General Engineering Contractor.
B -- General Building Contractor.
C-2 -- Insulation and Acoustical Contractor.
C-4 -- Boiler, Hot-Water Heating and Steam Fitting Contractor.
C-5 -- Carpentry, Cabinet and Millwork Contractor.
C-7 -- Low Voltage Systems Contractor.
C-8 -- Concrete Contractor.
C-9 -- Drywall Contractor.
C-10 -- Electrical Contractor.
C-11 -- Elevator Contractor.
C-12 -- Earthwork and Paving Contractors.
C-13 -- Fencing Contractor.
C-14 -- Metal Roofing Contractor. (No longer being issued)
C-15 -- Flooring and Floor Covering Contractors.
C-16 -- Fire Protection Contractor.
C-17 -- Glazing Contractor.
C-20 -- Warm-Air Heating, Ventilating and Air-Conditioning
Contractor.
C-21 -- Building Moving/Demolition Contractor.
C-23 -- Ornamental Metal Contractor.
C-27 -- Landscaping Contractor.
C-28 -- Lock and Security Equipment Contractor.
C-29 -- Masonry Contractor.
C-31 -- Construction Zone Traffic Control Contractor.
C-32 -- Parking and Highway Improvement Contractor.
C-33 -- Painting and Decorating Contractors.
C-34 -- Pipeline Contractor.
C-35 -- Lathing and Plastering Contractor.
C-36 -- Plumbing Contractor.
C-38 -- Refrigeration Contractor.
C-39 -- Roofing Contractor.
C-42 -- Sanitation System Contractor
C-43 -- Sheet Metal Contractor.
C-45 -- Electrical Sign Contractor.
C-46 -- Solar Contractor.
C-47 -- General Manufactured Housing Contractor.
C-50 -- Reinforcing Steel Contractor.
C-51 -- Structural Steel Contractor.
C-53 -- Swimming Pool Contractor.
C-54 -- Tile Contractors (Ceramic and Mosaic).
C-55 -- Water Conditioning Contractor.
C-57 -- Well Drilling Contractor.
C-60 -- Welding Contractor.
C-61 -- Limited Specialty.
ASB -- Asbestos Certification
HAZ -- Hazardous Substance Removal Certification
HIC -- Home Improvement Certification