Originally developed for commercial salmon fishing, many flashers do not perform properly at the slower trolling speeds recreational anglers use. There are a lot of flashers and other cut-bait holders available on the West Coast, but not all are readily available in Ontario, so I haven't had a chance to try the full selection. One readily available flasher that has proven itself to Great Lakes anglers is the Hot Spot. Constructed of plastic, its flex allows it to be trolled effectively over a wide range of speeds. It comes in a rainbow of finishes and several sizes, with the 11-inch model the standard on Lake Ontario.
Some anglers find that matching the colour of cut-bait holder and flasher to be the most effective.
If you're new to flashers, you'll notice that one end is wider than the other. Connect the narrow tapered end to the fishing line. From the wider rear section, attach a leader with a cut-bait holder. Vary leader lengths according to the salmon you're after. The heavy line is necessary due to the strain of the flasher and to help prevent line twisting.