What key is this?

What key is this?

I’ve had zero luck finding this in the help, in fact, what appear to be authoritative posts here don’t work for me. Perhaps more clearly, posting brics side-by-side requires …the use of a group bric found under… …or something very close to that (from memory).

I’m finding BLOCS extremely difficult. Perhaps because my vision of what I what and the templates are not remotely similar.

Can anyone help?
TIA.
Griz326

It’s the option (“alt”) key.