If you need strain relief on the feedline of your Field Dipole /Doublet you can use a small PVC Tee with a hole drilled in the top to allow it to slip over the end of a fiberglass pole.  The feedline can then be secured with nylon cable ties or electrical tape. Various PVC fittings and “Supreme Cork” synthetic wine corks make good  end-insulators.  I often just tie on fishing snap swivels so I can easily clip on some lightweight nylon cord to support the ends of the antenna.

I always use  Bowline Knots to tie the wire.