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From 1946 – 1949, Keymer worked as a salesman selling steel and steel-working machinery to companies and sheet metal installers. Housing construction was booming and gravity furnaces were being replaced with forced air furnaces. At the job site the installer had to customize parts of the ducts to fit properly and to circumvent obstacles. Many installers complained, saying they needed more than a screwdriver, pliers, snips, and sheet metal hammer to do the job. The few specialty sheet metal tools on the market were single-leverage tools and available at only a few outlets. Keymer’s designs employed compound-leverage. Squeezing the handles took only one third of the effort to do the same work compared to single-leverage tools, which the workers appreciated.

Most sheet metal installers work in the cold, as the heating system is not operating until they are done with their job. The use of cushioned handle grips on the tools not only cushioned the user’s hand against the bare steel, but also insulated the hand against a cold or hot tool. The grips were also non-slip. Sheet metal has oil on it and when handling it the installers hands would become slippery, so the non-slip grips were safer, too.

Like early automobiles, almost all hand tools in the 1940s were black or gray. Those were men's colors, the natural color of steel. Keymer was the first to employ color to distinguish between different types of hand tools – each having a different colored grip for easy identification in the toolbox. He bought garden hose in red, green, blue and black, cut pieces about 4" long, heated them in water and pushed the pieces onto the handles to make the grips.

The first Malco tools shared the same handles, or some were so similar they were hard to tell apart. It would be easy to grab the wrong one out of a tool pouch or tool box. The color-coding was a handy and practical feature to quickly identify the proper tool. While these were not ideas Keymer could patent, they show his pioneering spirit, leadership, and common sense.

When Keymer first introduced colored grips, he took a lot of ribbing. Many said he was making men's tools look like kids’ toys! But the idea caught on rather quickly. Tool companies now use color to distinguish their brand of tools from competitors. (The Wiss® brand color coded their aviation snips for the direction of cut.) And bright yellow and orange are used to make them highly visible. A brightly colored tool is easier to find, and less likely to be left behind or lost on the job site.

Malco was the first company to offer a complete line of sheet metal hand tools. The name Malco came from combining Keymer’s first name and the first name of an early associate named Al: Malco for "Mark and Al's Company" (it was Al's garage). Keymer invented more tools and sold tools invented by others if they would help workers do their jobs better or faster. Soon the manufacturing operations had to move from Al’s garage to the more spacious basement of Keymer’s Minneapolis home, where it operated for one year. In 1955, Keymer stopped selling for Minnesota Steel to run his business full-time.

Fueled by Keymer’s inventions Malco grew rapidly, requiring it to move every four or five years into a larger building. After occupying its sixth location in 20 years, in 1973 the company moved to a large building site near Annandale, where it has been able to repeatedly expand instead of relocating. New items have been added to the product line each year. Malco distributes thousands of products worldwide from its headquarters in Annadale. The company is now employee-owned and the largest employer in the Annandale, Minnesota, area.

Keymer served as Malco’s President until his retirement in 1978, at age 70. He died in 2001 at age 93.

Mark W. Keymer

(1908 - 2001) Mark Keymer designed all-new specialty sheet metal hand tools for fabricating and installing sheet metal duct work used with forced-air heating systems. In 1950, he founded Malco Products Inc. to manufacture and market his inventions. The company has become the leading supplier of tools and accessories for the heating and air-conditioning industry, and a major supplier for several other trades.


While not an engineer by education, Keymer was very practical and inventive in his designs. He designed the first compound-leverage hand tools, and was one of the first in the tool industry to use cushioned grips and to use color-coded grips to identify different tools. His early products included a metal-folding tool, a pipe crimper, a hand seamer, a snap-lock punch, and a notcher that made a V-shaped cut in one motion. These tools saved time and improved quality and consistency.

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