Wool

King Arthur’s Knights sat sullen eyed.;

“What ails thee all?” the Monarch cried,

Said one, “It’s this round table, sire.

The lads out there can’t feel the fire!"

Quoth Guinevere;

“Poor faithful knights, I’ll knit them all a pair of tights."

Morale was saved, which proved the rule:

There is no substitute for wool.