(as) plain as a pikestaff
US /əz pleɪn əz ə ˈpaɪk.stæf/
UK /əz pleɪn əz ə ˈpaɪk.stæf/

1.
sonnenklar, glasklar
very obvious and easy to understand
:
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His guilt was as plain as a pikestaff.
Seine Schuld war sonnenklar.
•
The instructions were as plain as a pikestaff, so I don't know why he made a mistake.
Die Anweisungen waren sonnenklar, daher weiß ich nicht, warum er einen Fehler gemacht hat.