"Gilbert loves to build things. Especially rocket ships - he loves building rocket ships."
"Gilbert lives in this house, which is next door to Mr Grenola's scrap yard.
Mr Grenola lets Gilbert help himself to all sorts of bits and pieces for his toy projects.
Gilbert helps Mr Grenola fix some cars and occasionally a washing machine or two."
Gilbert was never clearly defined other than what was written above, in the first two pages of the story and that the publisher wanted him to be a young boy.
Previous concept images sent to me depicted a boy in t-shirt with either shorts or trousers but nothing that would suggests Gilbert likes to build things, especially with scrap metal.
So I imagined, to a degree, what I would tell my daughter to wear if she had to traipse around a scrapyard and moving sheets of metal - Gloves, overalls, and goggles for the occasional welding (I thought about hard hats and boots too but didn't want to obscure him too much, though I probably should have given him boots).
Anyway I took that mental image at the time and produced a few sketches with a additional pencil behind the ear (to make him workman like) and imagined him keeping the goggles and pencil throughout the book. One of sketches I thought fitted well for the first page so it became the focal point of page one
To take what I did further I decided he looked too clean in the sketches so in the final image at the top I added dirt marks and paint marks, on his face and overalls.