Hard Lines

I had the following suggestion sent to me the other day. Although possible, the author admits to a guess. Any ideas as to the origin/first use etc? I couldn't find any documentation.

"I've often wondered myself about 'hard yards'.

A complete guess is that it comes from sailing ship days. Setting or taking in sails from the wooden cross-pieces, called 'yards', was arduous and
dangerous work - the more so the higher up a mast a particular yard might be. So to work on one of these might have become known as 'doing the hard yards'."

yardarm
\Yard"arm`\, n. (Naut.) Either half of a square-rigged vessel's yard, from the center or mast to the end.

Note: Ships are said to be yardarm and yardarm when so near as to touch, or interlock yards.

Source: Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.

yardarm
n : either end of the yard of a square-rigged ship

Source: WordNet ® 1.6, © 1997 Princeton University