Caster gauge for classic Mini ("Mini Cooper")

To measure the caster angle of a classic Mini, when stood on a reasonably smooth floor.

See https://www.theminiforum.co.uk/forums/topic/360471-using-caliper-bolts-to-measure-castor-angle/#entry3761930 for full details of how to use.

NB: the spirit level in the pictures is ONLY being used as a straight-edge: its bubble is not required in this application and it doesn't matter if the floor the car is standing on is not level, but the floor MUST be flat (planar).