Its your logbook, so write what you want. But, if it is one of your 4 qualifying jumps for BASE umber, it should be exctly what it is supposed to be, not a crane "attached to a building", or a dam that is "like a cliff" or a pillar that is "technically jumped like an antenna". If it is a jump not for number qualification, then write what you want, as for me, if it isnt one of the 4 its an other.