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MUSCATINE, Iowa — An Iowa teacher’s invention may now be considered by many schools across the country because of its legitimate potential to save lives if a person with a gun enters a school, looking for victims.

Gunfire in the hallways of U.S. schools has become an all-too-frequent occurrence, and in the wake of these often deadly shootings, novel ideas have been developed to keep kids safe.

A bulletproof backpack and ballistics blankets are just two suggestions that have become part of the debate.

Click here to read about the blankets.

Daniel Nitzel, an educator at West Middle School in Muscatine, Iowa., developed the idea for “The Sleeve” during the school’s active shooter drill.

The 12-gauge carbon steel case fits around the door’s closer arm, securing the classroom from the inside without the teacher having to go into the hallway to turn the lock. It can withstand more than 550 foot-pounds of force, making it nearly impossible to open the door from the outside, FOX 4 sister station WQAD reports.

“I think it’s a great product. It’s going to buy kids and teachers time for shootings,” Muscatine Police Chief Brett Talkington said. “These shooters [are] going to be pulling on the door. If they can’t get in, they’re going to move on.”

Nitzel said during teachers’ training they were told to tie a belt or a cord around the classroom door’s closer arm. He said it took a long time to get a cord, stand on a chair and tie the knot — and that wasn’t the most distressing part.

“I can tell you in our training, all five rooms that the teachers were trained in, the doors were breached. The cords were ripped and the officer who was portraying the active shooter came in and killed all of us,” Nitzel said.

Nitzel and his colleagues were inspired to form the company Fighting Chance Solutions. “The Sleeve” has been 10 months in the making, but it’s finally ready and waiting for patent.

A community college in Nitzel’s town is outfitting all their classroom and library doors with the device.