Hello Chris C
Most of our small trailers are built low to the ground for highway driving and to be towed by cars or low hitch vehicles. Anyone desiring to go off road or to rough areas drag body parts when they do. The high lift axles allow larger tires
and higher tongue heights for taller vehicles and better rough road traversing.
A typical low axle
is a drop type either spring mount with a upward bend in the axle
itself. or a tortion type axle
with a straight or upward slope on the torque arm. Mounting a spring axle with a streight axle would raise the ride hight, or reversing the drop axle would raise it even more. A tortion type axle would need to be replaced with one with a steeper downward torque arm would do the same thing. The various angles range from 22 degrees up angle for lowest ride to a 45 degree down angle for the highest ride without raising the frame with spacers.
Some links have been posted explaining this better than me but I dont know how to reference them.
Hope that helps, Others can give more detail.