A wick is a stable or oscillating linearly repeating pattern that can be made to burn at one end. The essential characteristic distinguishing it from an agar is that it is one-dimensional. A fuse is quite similar, but is expected to actually burn and thereby decompose.
Conversely, a wickstretcher is a moving entity, usually a spaceship, which lengthens the segment of wick to which it is conjoined. Various combinations are possible: two stretchers moving in opposite directions could prolong a finite wick; one end could possibly be freestanding, or even require stabilization, a service rendered by a fencepost.
Finally, a wick could simply be infinite in extent, possibly quite convoluted in the style of a Hilbert curve. Or without any evident termination except for possibly closing into a loop.