I found this on the Harken
Springs & Boots
Should I use a stand-up spring or boot?
Both stand-up springs and boots are used to keep blocks from hitting the deck
. Stand-up springs are stronger and stiffer than boots, but boots can be used in a number of situations. For example: If the line might foul in a stand-up spring's rings, you can substitute a boot.
What is the simplest way to install a stand-up spring or PVC stand-up boot?
Take two zip ties and loop them through each side of the spring (or PVC boot). Pull the zip ties taut until the spring (boot) compresses. Now you can easily attach the block to the eyestrap, padeye, etc. After you attach the block, cut the zip ties and the spring will pop back into place.
Tip: Instead of wrestling the block onto a stiff piece of PVC, soften the boot with a hair dryer (don't burn it), or soak it in warm water
. This makes the boot much more pliable and easier to manipulate. When the boot cools, its shape returns to normal.