bollard pull

[druiaghtagh]

Little tug boats move enormous ships, just read something in a book about one having a bollard pull of 160 tons , what does that mean please?

[Clanad]

The capacity of a tug to pull weight, measured in tons. The capacity is determined when a tug is secured to a dock by a rope and the boat�s engine is fully engaged.
See:
www.seacoastonline.com/news/07032005/accent/50917.htm