Correct course of action for failed electrical work.

[Fastpedeller]

I (could have) had a similar experience with a 'roofer' - young lad came to estimate for roof on a 6m x 2.7m rectangular extension to be tied in at right angle to existing roof. I took him around the side of the bungalow so he could see the ( very large) roof trusses that had been delivered. I explained "there's 11 trusses there, 6 one size and 5 reducing down in size" (or similar. I can't recall exactly). To which he asked "which way round do they go?".
I said " I'll give you a clue,the extension is 6m x 2.7m, and the largest trusses are 6.6m long" He had a blank look on his face. I ended the conversation there, as it was clearly his first roof.