Fold flat walking or jogging strollers, as well as various fold flat cargo carrier devices are disclosed, which include at least three wheels which may have pivoting wheel support units and alternative foldable support frame embodiments are disclosed. The wheel support units include, in various embodiments, simple manually manipulable methods to latch each wheel in the operative or stowed flat positions, which effectively allows the device to fold to a flat profile without any part or wheel being detached. Associated innovations include a unique forward wheel folding system, a pivoting or floating transverse axle replicating unit ("false axle"), which pivots and latches to replicate a typical fixed wheel axle, but conveniently pivots to a fold flat stowed position. The innovations may also be applied to miscellaneous other types of wheeled carrier devices besides strollers, such as gurneys, golf bag carriers, and hunting game carriers as several examples, and also parking brake and alternative latch release methods are disclosed.