CV joint boot slider tool

[amacman]

can anyone explain to my weary head how these cvj boot slider tools work
i was looking online for boot clamp tool when i saw the bootslider which apparently fits new boots without the need to remove the axle or separate the cv joint .
i`m baffled as to how that works without using a split boot .

[amacman]

ok, looked again , info says no need to remove axle from vehicle but i think you need to separate relevant cv joint , just not remove bearing part , cut off old boot and connect air line to tool which expands small end of boot to slip over bearing.
i`ll give that one a miss and just remove bearing as per normal .