Although about 110 years old, this was used to install tongue-n-groove flooring and still seems to be functional. The first cog is turned via a lever which latches between different teeth each time the handle is swung. That cog turns the big central screw, which moves a bracket and I expect that increases pressure on the edge of a floorboard. I guess the 2 partial cogs grab onto another floorboard(?).

Weight: 8 kg. Dimensions: 73cm x 29cm x 19cm.

I'm going to sell more interesting antique/vintage items (plus Kauri Gum and Greenstone), so you might like to save me as a favourite seller :-)

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