The wheel’s axle rod had to pass through the two diagonal supports. A brace and a drill bit the same diameter as the rod was used to bore the hole. I made a mountable square out of a scrap piece of wood that clamps to the supports for drilling guidance.
The auger bit was too short to drill into the second support and so I had to drill in from the opposite side and hope the holes lined up! They did – but only just. I had to hammer the rod to get it though both holes – it was a very tight fit. This made the end of the rod mushroom and so I had to file it down again to get the wheel onto it. Stop collars on either end and a washer between the wheel and the frame finished the job. Well, actually hacksawing the rod to size finished the job. Followed by a cup of tea.