Advice on how I can Extrude Cut on an angled Helical Blade Surface?

Hi Everyone,

I am trying to extrude cut a 0.8cm by a 0.4cm rectangle on an angled helical blade and I can't seem to make it work. I had already done one on the top of the blade and trying to figure out how I can mirror another one at the bottom.

Able to assist and advice!

To  &‌, Thank you for your help regarding my previous queries. I try both method and both works! Thank you guys so much! Hope you can assist me again

Thank you all!

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