Why won't axle rod go through wheel?

 The say that if you put questions in your website text then it is more likely to be found by search engine. Hence the title to this post. This is whet I searched for but although I found many people with the same problem I found no answer. I used about 8 hours trying but the rod just wouldn't go through. I used a slightly smaller rod as a guide but still no joy. Eventually I realised that the rod would not pass through the small spacer. Eureka, I had swapped the spacer with the washer. The rod passes through the space but only the threaded part goes through the washer. Satisfied at slving the problem but frustrated that it took so long.

I don't want to look at that axle so I'm posting a photo of the bike with newly painted tank. Nowhere near this stage yet but I like looking at it.