A suspension platform system having a work platform suspended between a sinistral modular mast and a dextral modular mast by a hoisting system. The modular masts are composed of at least two mast units stacked vertically and attached to one another. Each mast unit has a multifunction rail including a plurality of safety engagement devices and a stabilizer guide device, and a unit interconnection device. The work platform has at least two mast stabilizers that cooperate with the stabilizer guide devices to prevent undesired swaying of the suspended work platform. The work platform has a plurality of platform mast engagers cooperating with at least one of the mast safety engagement devices to releasably lock the platform to the modular masts. The hoisting system includes multiple carriages, hoists, and mast cables. Each carriage engages the associated mast so that the carriage may be conveniently slid up and down the mast.