Dave Felkel took what he called a “half-court buzzer-beater shot” to create Guarantee 3, his basketball skills development product.

Last year, Felkel, who runs a La Canada construction business, took a second mortgage on his home to get the $120,000 he needed to create Guarantee 3, which he claims will dramatically improve a player’s jump shot and dribbling. The device has an elastic band that connects a fingerless glove on the user’s shooting hand to a vest. The resistance helps the user build strength while developing basic basketball skills.

Felkel sold his first unit in August, and since then said he has sold about 3,000 of the $35 harnesses, which are manufactured in China and packaged in the United States. Most of the product has sold online and at events, and he is working on getting it into big-box retailers.

Initially made out of an assortment of household items, the device was created to help his son learn how to shoot.

“My son told me he had a really weak jump shot one day. So I bought backpacks, stretch bands and gloves to help him develop a shot,” Felkel said. “My product was made to teach basic fundamentalbasketball. In America, we don’t work on techniques.”

He showed the cobbled-together device to several coaches and chiropractors, who he said were supportive, prompting him to go all in on the development.

Felkel offers instructional videos on his website for people to learn how to shoot properly and practice with the product.

Still, skeptics such as Sander Hermann, a professional basketball shooting coach in Orange County who has worked with such high-profile players as Los Angeles Clippers star Blake Griffin, believe only a proper coach can help a player learn to shoot consistently.

“Shooting comes to down to coaching. You actually have to teach people. I look at 15 different things when I’m teaching,” Hermann said.

– Justin Yang