COLREGs
Day Shapes Explained — Balls, Cones, Diamonds and Cylinders
Published · Last checked October 2026
By day, vessels hoist black shapes to show what they are doing. One ball means at anchor, two balls not under command, three balls aground, ball-diamond-ball restricted in ability to manoeuvre, a cylinder constrained by her draught, two cones points together fishing, a diamond towing (tow over 200 m) and a single cone point down a sailing vessel using her engine.
| Shapes | Meaning | Rule |
|---|---|---|
| Ball | At anchor | 30 |
| Ball, ball | Not under command | 27(a) |
| Ball, ball, ball | Aground | 30(d) |
| Ball, diamond, ball | Restricted in ability to manoeuvre | 27(b) |
| Cylinder | Constrained by her draught | 28 |
| Two cones, points together | Engaged in fishing | 26 |
| Cone point up, in addition | Fishing gear extends more than 150 m in that direction | 26(c) |
| Diamond | Towing or being towed, tow longer than 200 m | 24 |
| Cone, point down | Sailing vessel also under power | 25(e) |
| Three balls (masthead and both yardarms) | Mine clearance: keep 1000 m clear | 27(f) |
The dredger
A vessel dredging or working underwater shows ball-diamond-ball, plus two balls on the side where there is an obstruction and two diamonds on the side you may pass. Remember: pass the diamonds.
Do yachts need to show them?
Yes. A yacht at anchor should hoist a black ball forward, and a yacht motor-sailing should show a cone point down. Small vessels are exempt from some shapes: a vessel under 7 m at anchor away from channels and anchorages, and a vessel under 12 m aground, do not have to show them.
Test yourself with the day shapes quiz and print the day shapes cheat sheet.
The rules behind each shape
- Rule 24: Towing and pushing
- Rule 25: Sailing vessels underway and vessels under oars
- Rule 26: Fishing vessels
- Rule 27: Vessels not under command or restricted in their ability to manoeuvre
- Rule 28: Vessels constrained by their draught
- Rule 30: Anchored vessels and vessels aground