Help required to identify two John Heath Kit parts

[Nick Lettington]

Are there any other parts with three corresponding holes? If they aren't countersunk for wood screws, are they for spreading load... how many fixings pass through the windscreen uprights where they bolt onto the sides of the scuttle, for instance?

Also consider what a riser is... or could be? Unless colloquially people call shims or packers "risers" which wouldn’t be helpful, a riser is generally a vertical board on a step or the front panel of a seat perhaps...