I use a PVC arch across my vegetable garden and support my vining plants from that archway using a makeshift trellis.  The Tee fittings on this have a tendency to snap after a year in the sun, as they are a tress concentrator, especially as the vining vegetables begin to bear fruit and get heavy.

This little device lets me easily spread that stress over a larger area away from the actual PVC joint by using a cutoff end of some fiberglass rebar, suspended in the joint with a zip tie (makes for easy disassembly at the end of the year, too).  I threw it together in about 15 minutes in Shapr3D and sent it over to the CoreOne to crank out enough of each for me to replace all the fittings in my garden.

Assembly is easy, with just a little effort to push the support into the middle of the Tee or Cross fitting, with the rebar pass through facing out.  Snug up a zip tie or bundle of tape around the rebar to make a 'stop', then slide the rebar into the fitting until it is resting vertically on the zip time and suspended through the PVC fitting.

The brace is designed to have it's ends slip fit into the PVC pipe, as well, allowing any load to be spread across the whole fitting and into the connecting pipes.  

I have included both Cross and Tee fitting examples.

Enjoy!