Rules of the Road · NUC / RAM / Constrained by Draft
By day, a vessel not under command shall display:
- AA black cylinder
- BBall, diamond, ball in a vertical line
- CA single black cone, apex up
- DTwo black balls in a vertical line✓ Correct
Explanation
Rule 27(a)(ii) requires a NUC vessel to show two black balls in a vertical line by day — the daytime equivalent of the two all-round red lights. Two balls means 'helpless'; three balls means 'at anchor.'
Authority: 72 COLREGS Rule 27(a)(ii)
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