The Innovator Plus Tie Rod is the all-thread screw that goes through the picker drum, holding 17 discs together - or 1/2 of an Innovator Plus Picker drum.  There are 4 tie-rods per 1/2-drum.  Each tie rod comes with a clamped-nut end and screw-on nylock nut.  Tie rods are sold as a set of 4.