I tend to use tippex.
Plumb your main line, mark on the rod with tippex where the top of the float comes, and then plumb a second line and do the same. Then you can change between the two swims by just moving the float as and when required.
i allways plumb up before i put any feed in this way it would not
disturb your feed .
also plumb the area around in front of you you would be supprised by the differences you can get you can also find the edge of drop-offs,
bottoms of slopes ect which are all good spots
heres a tip
when plumbing a lake with weed on the bottom
get a piece of rubber about two inchs long put two cocktail
sticks through the rubber criss cross and add a 1bb shot into the rubber the sticks will rest on the weed and you get the right depth
instead of the plummet going through the weed
good or what