'To rig a purchase' definitions:

Definition of 'To rig a purchase'

From: GCIDE

Rig \Rig\, v. t. [imp. & p. p. Rigged; p. pr. & vb. n. Rigging.] [Norweg. rigga to bind, particularly, to wrap round, rig; cf. AS. wr[imac]han to cover.]
1. To furnish with apparatus or gear; to fit with tackling. [1913 Webster]
2. To dress; to equip; to clothe, especially in an odd or fanciful manner; -- commonly followed by out. [1913 Webster]
Jack was rigged out in his gold and silver lace. --L'Estrange. [1913 Webster]
To rig a purchase, to adapt apparatus so as to get a purchase for moving a weight, as with a lever, tackle, capstan, etc.
To rig a ship (Naut.), to fit the shrouds, stays, braces, etc., to their respective masts and yards. [1913 Webster]