WM15A-90 is designed for horizontal use, WM15A consists of one 3 foot long vertebrae carrier and 15 individual vertebrae pieces. Each vertebrae has four separate channels to carry wires, two main channels and two smaller ones. The two main channels open from the side and then snap back closed. Wires on top sit in a 1/2" deep trough. WM15A meets requirements for cities specifying that wires be carried in separate channels.