I made this Bobbin few years ago, its a bamboo bobbin with variable weights inside, they are actually what I call “Ostrich Shot “ a bit bigger than Swan shot. Makes it easy to adjust the weight for shy biting fish.
If I am roaming around , I sometimes cannot be bothered with chains or tethers on bobbins, I just use a piece of plasticine squeezed
on the line, at night I just push a starlight into the plasticine . Simple and works very well indeed as I can again adjust the weight to suit conditions.
A third “bobbin” I sometimes use in an emergency . I simply just cut a length of twig from a handy branch, push a slit into its end grain and trap the line through the slit. Again, works very well.
There must be dozens of different types of bobbins. It seems the “modern “angler needs something very high tec, but in reality they do no more than anything posted so far, bite alarms and their accoutrements excepted of course.
David