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CMI Pro Knot


Front Rear
Front Rear
Top Open for Rigging
Top Open for Rigging

Technical Details

I acquired my CMI Pro Knot in 2017 as part of Bob Thrun’s collection.

My CMI Pro Knot is 80 mm. long, 80 mm. wide, 29 mm. high, and weighs 448 g.

The CMI Pro Knot consists of two eccentric cam "ascenders" fastened back-to-back with three countersunk hex screws. Each ascender consists of an extruded, anodized aluminum shell, a cam assembly, and a set of straps and buckles. The frame has a 16 mm. attachment hole at the base. The rope channel is 18 mm. wide, and is 57 mm. from the cam pivot. The cam is spring-loaded and has a (4.3)^5(4) tooth pattern. The cam radius increases from 43 to 62 mm. over a 46° arc, giving an effective cam angle of 24°. A spring-loaded safety on the base of the cam blocks cam opening unless swung out of the way. When the cam is open, the safety may be released to catch the shell, holding the cam open.

Each side is printed with "Made in USA," "LIMB" (not "CLIMB"), "↑," and "Max Limb Weight 500 pounds."


The Pro-knot is not an ascender, it is a mechanical knot to be used by arborists when lowering limbs. Since I don't swing through trees, I'll let them evaluate it for their purposes, and will refer the reader to the instruction manual that comes with the Pro Knot.

The ascender bodies are milled from the same shape extrusion as the CMI foot ascenders are, and the Pro Knot uses the same cams and cam safeties as well.

The Pro Knot can be disassembled to produce two hand ascenders. These ascenders are inefficient because the tie-in point is well-separated from the main rope channel, causing the ascender to tilt when loaded, resulting in considerable lost motion.

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