I Am Puzzled

[excelsior-1]

When the inventor of the drawing board messed things up, what did he go back to?

[frugalfred]

The best thing before sliced bread.

[bibblebub]

square one

[tonyav]

The slate !.

[AB Editor]

I imagine he chalked it up to experience.

[tonyav]

Groan.

[Baldric]

Bit sketchy excel!