The wrong housing insert fits rather nicely

Yes. The stamped number is underneath. You can identify the insert perfectly after taking the whole thing apart. Our recipe names are just small and large.

Move the identification into view and use matching names on the recipe list. That helps people check, but the reversible mounting still needs attention.

Toolroom suggested moving one locating pin off centre. Both insert families would keep the same new mounting pattern. That should sort the backwards fit, at least.

And which bit stops me choosing the wrong family?

Try both wrong combinations on the drawing before anyone drills anything, because a new pin can still leave you with two equally convincing wrong choices.

Robin's question needs its own answer. A direction key will not identify the family. Can your changeover check compare the actual insert with the selected recipe?

We put a number beside the handle. Underneath was useless with gloves and a full bench.

Our proposed check only sees an insert present. I've asked controls about reading its identity. Fiona, thanks for the handle idea. There is room there.

Does lifting it out cancel the previous check?

It will in the revised sequence. Toolroom has drawn the direction key and readable number. Automatic identity checking is still a proposal, so we're not releasing the changeover yet.

Use one naming scheme in stores too. The spare insert is where a beginner may first meet these names, long before the recipe screen.