Swedish to English Social Sciences Social Science, Sociology, Ethics, etc. The use of LEGO as a metaphor

This comes from a methodology textbook where LEGO is used as a metaphor. In one instance, the text refers to one kid asking another for an "etta" (i.e., a piece with only one dot). This was the only picture I could find in a quick search: https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTVp8AL...

I'm sure there is a good way of describing this in English, but it would be great to use the term used colloquially by English-speaking kids. When I was a kid growing up in Sweden, everyone knew exactly what you meant when you asked for an "etta." :-)