This circuit made from three 12V DPDT PCB (printed circuit board) relays turns your rear turn signals into additional brake lights while allowing them to still function as brake lights.

I soldered wire to the appropriate relay pins, put pieces of popsicle stick between them, wrapped them in electrical tape and then filled the tape with epoxy to hold them together and waterprofo them. Finished product:

 

© 2013 Drake Smith - Please do not use or reproduce this elsewhere.  Feel free to link to it though.