This is an imaginary situation, but it's based on past real discussions. I imagine a lot of conversation about the names of computer keys and probably some brainstorming. We might talk about using "the" with the names of keys, since each one is unique on a keyboard. I could see shifting to a discussion about the birth of compound nouns and how their spelling changes as they become solidified in the language (space bar, space-bar, or spacebar?). Lots of sloppy scribbling might happen in the working area of the board, but I imagine pausing to clean it all up ... maybe small groups could compare their notes and develop a summary for that space themselves, then share and compare as a class. Maybe there would be a graphic organizer, a Venn diagram, or a table. Language conclusions would go in the lower right corner. Learner-selected words to study (chosen from the many discussed) would get copied to the right. In this dream-lesson, learners decided to highlight compound nouns, since that's also the form we discussed. They chose "space bar" because it's got a special name other than "key" and they chose "tab key" because it's an example of the way to name most of the other keys on the board, plus the word "tab" was new.
This is just current thinking ... I thought I'd share the two-page idea right away, for what it's worth. Note that the "pages" are labeled 1a and 1b. That's so we can take pictures of half the board and be able to put the pictures into the correct order later (after erasing, the next board would be labeled 2a and 2b).
I'd be interested in feedback!