1) Commonly used by dialect speakers in the phrase 'by the rack of the eye', that is estimating an angle or a distance without any rule or measurement. No early example has been found but 'rake' was formerly used in estimating distances.
2) A frame designed to hold a cross-bow when it was not in use.
1520 To Mr Vavasour my crosse bowe with rake, York
1548 a crossebowe with the rakke for the same, Norton, Wath
1565 a crosbowe & rack xxs, Temple Newsam.
3) A bar or set of bars used to support a spit or other cooking utensil.
1400 Et respondent ... pro ij paribus de rakkez, j brandereth, Richmond
1434 unum yren spytt, duos yren rakkes, Campsall
1535 ij pare rakes of Iron iijs, Stillingfleet
1567 fowre spittes two Iron Rackes, one gyrde Iron, Fixby
1669 a rainge, a pair of racks and 3 spits, Elmswell.
4) A verb, descriptive of the gait of a horse when the two feet on each side are raised simultaneously.
1490 all my riding horses ... except the raking gelding, Batley
1549 my yonge daple gray geldyng rackyng and trottyng, Newby near Topcliffe
1562 one trotting mare ... One old rackynge nagg xxs, Thrintoft
1631 one sad bay maire trots ... one bay fillie with a white starre racks, Adwalton.