I ride at all hours of the day and night and wish to stay alive so I like to try and make sure I can be seen on the road. I like to double up on my rear visibility just to be extra sure approaching vehicles see me. I purchased some standard rear lights that are meant to fit around round posts, but not everywhere I wish to place a light on my new bike is nice and round. Here is the light and the bracket mounting stuff it came with.
And as I said, it is perfectly suited for nice round posts, like a seat post where I did secure one.
But I wanted to double up and although the Topeak rear rack has some holes in the back of it to screw things through, my light was not a suitable match since it does not incorporate a doodad that will allow it to be secured through a hole. This is where the venerable zip tie once again comes to the rescue. I strung a zip tie through the clip on the back of the light that is meant to slide into the bracket that came with it and looped it around the back of the rack.
To be doubly sure I used two zip ties and that should ensure that it not only stays secure, but does not walk away when I am gone.
Two lights, two more zip ties. Total zip tie count to date: 6.

Good luck. I've gone through 5 or 6 of those ViewPoint lights. All it takes is a good rumble (e.g., on the W&OD Trail at the Goose Creek bridge or the Sterling Blvd. crossing) and they jump right off the bike. They rarely survive the impact intact, and once you glue the red part back together, it never holds quite as well again. I'm currently using an Axiom Zap (http://www.performancebike.com/bikes/Product_10052_10551_1112122_-1_400903_400014_400159), it's both brighter and more inclined to stay attached. Plus, it's rechargeable.
Posted by: Ross | 10/31/2012 at 10:48 AM
#facepalm Just realized this blog isn't the Washington-DC-local one I thought it was, so the local references are meaningless. Sorry!
Posted by: Ross | 11/01/2012 at 09:33 AM
same experience here
that's why i have them only attached to my luggage or clothes.
Posted by: mike | 11/01/2012 at 03:18 PM
That's how I've attached a NiteFlux Red-Zone-4 to my rack. With that light, it works great.
For PBSF type lights, I've got a rack-adaptor.
Posted by: atom | 11/02/2012 at 03:23 AM