a sinker or float that releasably clamps around a line , such as a fishing line , including two members shaped to define a channel for the line when in a closed position . a locking means is provided to releasably lock the two members in the closed position . each of the members has at least a portion of high or low density material to provide a sinking or floating effect . a jacket may be provided that retains the high or low density material therein . the jacket may also include a hinge portion such that the two members can be hingedly opened and closed .