By STEPHEN REGENOLD

Like many inventors, Brian Dagnon took the vague sketch of an idea and pieced together a prototype using available parts found at a hardware store. His crucial off-the-shelf item — an inexpensive retractable keychain device often used by janitors — would be paired with climbing webbing to build a new type of dog collar that would eliminate Dagnon and his dog’s dependency on a leash.

From that first rough prototype, Dagnon refined his concept and eventually built a small company to sell a marketable iteration of his collar design. The Release N Run collar takes cues from that janitor’s keychain, including a small reeling mechanism that retracts a cord, to offer a collar with a tiny, spring-loaded leash hidden inside.

The company, Rad Dog LLC, is based in Bellingham, Wash., and its products are made for the “mostly off-leash dog,” as a company tagline puts it. The Release N Run collar was designed for people who frequent dog parks and natural areas where you don’t need a leash.

On the collar, a thin cord serves as the leash. It’s four feet long and has a loop on one end for a handle. The other end is tucked inside a pocket on the collar, where it automatically winds unseen into a mechanical retractor device when you let go.

I used the collar with my dog, a 100-pound Weimaraner. An average walk near my home includes sections of woods where I let the dog run free. The Release N Run was a nice alternative to bringing a normal leash along that I would regularly have to carry.

Another point with the collar: Your dog will always have a leash on. Though hidden and out of the way, the Release N Run collar gives instant access to a leash in order to control your dog in a snap.

The leash looks thin and string-like. In fact, it is thinner than many shoelaces. But Rad Dog LLC uses Spectra in the cord, which is a polyethylene-based super material stronger for its weight than steel.

The Release N Run collar is made in the USA. It is a solid product and a great solution for anyone who hikes or runs with their dog off leash. At $32.95, it’s not a bad price either.

The only cons I discovered were an occasional tendency for the leash’s handle loop to stick out of the collar pocket a couple inches. When it snagged like this and did not retract fully, my fear was that the handle might attach itself inadvertently around a tree branch or in the brush as my dog ran.

Otherwise, the collar performed fine. My dog did not mind wearing it, even with its slight bulge where the mechanism sits. He loves any walk on a leash. But like most dogs, his real joy is when I let go of the leash and relinquish control, the snap of the Release N Run collar a signal to bound away, sniff, run, jump, and be free.

—Stephen Regenold is founder and editor of www.gearjunkie.com.