dragons came flying to many of the plain cave-mouths near-by , carrying netting full of men , whom they let down inside the caves just as the aviators had been deposited : the dragons had a sort of trick of setting their hind legs upon the lip of each cavern , and setting their foreclaws into some ridges carved above the mouth , while their riders unhooked the netting , so they did not have to squeeze into some of these smaller caverns .