It basically is a monopoly of sorts. In fact, it's a business of giants:
Stanley Black & Decker owns Blackhawk, Bostitch, Facom, Mac Tools, Proto, Sidchrome, Black & Decker, and Stanley Hand Tools.
Ideal Industries owns Pratt-Read, SK Hand Tools, and Western Forge.
Textron owns Greenlee, Klauke, and Paladin Tools.
Snap-on owns Bahco, CDI Torque Products, and J.H. Williams Tool Group.
But then there are the real giants:
Danaher Corporation owns Allen, Armstrong Tools, Easco Hand Tools, GearWrench, K-D Tools, and Matco Tools.
...which merged with:
Cooper Hand Tools which owns Crescent, Lufkin, and Xcelite.
...the merger of which lead to the creation of:
Apex Tool Group (a joint venture of Cooper Industries and Danaher.) It was formed by the merger of Cooper Tools (Cooper Hand Tools and Cooper Power Tools, which manufacture hand tools and power tools respectively) and Danaher's Tools and Components segment. Apex Tool Group owns:
Allen - Hex keys
Armstrong Tools - Industrial hand tools
Atkins - Hacksaws
Belzer - Mechanic's hand tools
Campbell—Manufactures chains and clamps.
Caulkmaster—Pneumatic dispensing guns.
Collins - Machetes, shovels, and axes
Crescent—Produces general hand tools and tool sets.
Delta Consolidated Industries - tool boxes
Diamond — Horseshoes and farrier tools.
Erem — Precision pliers.
GearWrench - Ratcheting wrenches and hand tools
H.K. Porter — Bolt and cable cutters.
Iseli - Precision matched parts
Jacobs Chuck - drill chucks
Jobox - tool boxes
K-D Tools - mechanic's hand and specialty tools
K&F - files and rasps
Kahnetics—Dispensing systems.
Lufkin — Calipers, gauges, micrometers, and measuring tapes.
Mayle - Mechanic's hand tools
Nicholson — Produces files, rasps, and saws.
Plumb — Striking tools, such as hammers, axes, and chisels.
Sata - Mechanic's hand tools.
Spline Gauges - gauges
Weller — Soldering tools. Acquired by Cooper in 1970.
Wire-wrap — Electrical connection equipment.
Wiss — Scissors and snips. Acquired by Cooper in 1976.
Xcelite — Electronics tools such as general and specialized screwdrivers and pliers.
Airetool - tube cleaners and expanders
Apex - fastening tubes and universal joints
Buckeye - material removal tools, fixtured drills
Cleco - assembly tools
Cooper Automation - automated fastening systems
DGD - automated systems
Doler - advanced drilling equipment
Dotco - material removal tools
Gardner Denver
Geta
Master Power - industrial air tools
Metronix - Servos, drivers, and speed controls
Quackenbush - advanced drilling equipment
Recoules - drilling tools
Rotor - assembly equipment
Utica - torque measurement and control tools