People sometimes ask about how to use llRezAtRoot and the related llRezObject, and particularly about how to position the rezzed object in relation to the rezzer, so that no matter how the rezzer is placed, the rezzed object always ends up in the same position, and looking in the same direction, relative to the rezzer, rather than, for example, always rezzing n metres north of the rezzer and looking south (which will probably place the object where you want it to be when the rezzer is rotated at