Locking plug to hold this Michelin foot pump closed.

The elongated faceted knob lets your fingers (and eyes) know from its orientation when you’ve engaged the lock, and the faceted shaft locates positively when turned.  And a colour other than the pump’s original black is less likely to get lost!

WARNING: the plug will spend most of its life with a strong shear force applied to it, and if it should fail with time, or for PLA with temperature, the pump could fly open unexpectedly and forcefully, possibly causing damage or even injury.

Print settings

Print in the supplied orientation, using supports, so that in use the shear force presses the layers together rather than shearing them apart from one another.

Use a layer height no more than about half the line width, so that half an outer wall line is supported by the previous layer in the 45° overhangs.

Print inner before outer walls, for the overhangs.

Print solid, using Lines of alternating directions, for maximum strength.

How I designed this

In FreeCAD.  The .FCStd model file is attached.