A system of controlled translocation of macromolecules by gel electrophesis employs a funnel nanopore structure. The sampling clock is controlled so that the time delay between the transmitter and the receiver is effectively eliminated. A pin may be placed in the passage such that a first portion extends away from a front of the housing and a rear portion extends away from a rear of the housing. Each of the motor-vehicle-mounted trailer alignment unit and the trailer-mounted motor vehicle alignment unit includes respective adjustable-length riser portions that facilitate efficient adjustment of and use of the alignment apparatus.