sentences:  The original non-directional markers in cave diving were clothes pegs, but the circular plastic "cookies" were developed later, based on the successful line-arrow design, and are more secure when placed on a guideline.They can be used to mark reference points, to distinguish lines at an intersection, or can be placed by each member of a team on a jump or gap line to identify who is still on the line if the team gets separated.As they are commonly used to identify the presence of a diver, they generally have some kind of personal identification, such as initials or drawings and may have notches, or holes added so they can be identified by feel.