I like to think that “knotty” as a descriptor came from the wood workshop. Before power machinery, a board slightly too wide or thick would be planed down to a precise dimension. Only, wood planes are hand held devices, with a very sharp blade, adjusted very precisely.

And when the blade of the plan is sliding down the board, gracefully parting the grain and peeling off onion-skin thick slices or respectably heavy gouging – until you hit the knot. The grain of wood no longer lies along the board, the density of the wood is no longer uniform in the direction of travel. Sap may have gathered to stick to the glossy sole of the plane, or hardened to a surprising degree. Stopping the plane mid-board is always a disappointment, as the blade breaks off the curling wisp of the removed material. Restarting the operation mid-board is seldom as graceful and smooth as a full-length pass; a gouge is likely where the blade stopped, another likely where the repairing stroke begins.

A knot usually stops the plane. With ill luck, you might have to clean sap off the plane to operate smoothly against the board again. You might also damage the blade, turning or breaking off a small section of the blade – resulting in a gouge or ridge following the plane.

Now that we use power equipment, the chance of blade damage and gouges and ridges are still a likely hazard of working the knotty board.

Perhaps it is the dismay and frustration of the craftsman over damage to the blade of his tool, over having to divert time from the work at hand to re-dress and possibly rebuild his tool. When dealing with a fundamental difficulty with unexpected intrusions of adamant elements, requiring that the tools – the arguments and beliefs – be reworked, maybe repaired, that earn such difficulties the accolade of a knotty problem.

Or not.