When using a lightweight doublet antenna in the field you often need a simple means of attaching the centre of the antenna to a fiberglass mast (I use the Shakespeare 20 foot Wondepole Crappy Pole). Attaching antennas to the eyelet at the tip of a pole usually results in some part of the tip eventually breaking.  The solution above shows how to make a simple centre support using a fishing snap swivel and a crimp ring terminal . The the bottom of the snap swivel is at the centre of a “Electricians Knot” used to tie the two halves of the wire doublet together.  I can’t take credit for coming up with this idea (it came from someone on QRP-L) but I have used it a lot and it works very well.