Third, but maybe most relevant to Rodney's requirement:
This is the system used to lock the slides on my BCA 'Jig Mill'
The loose piece is shaped to match the dovetail angle, and features a small ridge on the underside.
It is pulled into firm contact with the dovetail as the screw is tightened.
MichaelG.
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Pick'n'Mix from those, Rodney … unless someone can suggest a better lock for your shaper.