Making a depth gaugeThis is useful for measuring indentations such as the amplitude of ripple marks or the anterior groove of echinoids.RequirementsTyre tread depth gaugePiece of wood 20cm by 5cm by 2cmDrill a hole in the centre of the piece of wood so that the tyre depth tread gauge fits tightly into it and the bottom is flush with wood. The tyre gauge should read zero when the wood is resting on a flat surface.depth gauge