Drift (thing)

In wooden ship construction, a drift is an inexpensive fastener used to hold large blocks of wood together permanently.  They are long (sometimes more than a yard long) wooden or metal rods, hammered deep into both pieces of wood.  They fasten together pieces of wood that will never be separated through the lifetime of the ship:  big keel timbers, or planks edge-set to make rudders, centerboards, or hatches.

Drifts can be cut from lengths of soft metal rod (rebar would be nice if it weren't iron), with barbs quickly knocked into the sides with a cold chisel.  They can also be rough-cut wooden dowels, without any special effort given to rounding off, although a broom handle will do in a pinch.  Installing a wooden drift (aka 'treenail') is literally banging a square peg into a round hole.

Drifts are decidedly low-tech, but they work:  Friction on the sides of each pin holds the pieces of wood together snugly.   When the wood gets wet, it swells up and the drifts are held in that much more tightly.

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Several drifts can be set into a line, but always at the same angle.   It's geometrically impossible to set drifts at different angles before putting the two timbers together, and while it is theoretically possible to drill in from the other side of one of the timbers afterwards and set another line of drifts at right angles to the first, the swelling of the wood would then make the drifts tear the timbers apart.