A "T" is an intersection of guidelines. You must mark every "T" so that when you come back to it there is no way to make a wrong turn at the intersection and end up out of air before you're out of cave. "Dropping a cookie" means attaching a circular marker to a line at a "T" to mark it.carldarl:Sorry if this is a really dumb question but I'm not trained in cave diving. Can you "BRIEFLY" describe what doing a 'T' and dropping a cookie are?
Rick