A US father has invented a new style of doorstop he believes will save children’s lives by blocking gunmen trying to get into classrooms.

Ryan Bowman was inspired to act after last year’s mass shooting in Parkland, Florida that killed 17 people and wounded another 17, as well as the 2012 massacre in Sandy Hook, Connecticut, in which 28 people died.

He has invented a “safety wedge” to block anyone trying to push their way in.

It differs from a conventional doorstop, he says, because its rubber rib structure provides additional stopping power, and it also folds up, creating a more secure block.

It is designed not to budge even if someone pulls on it after it has folded.

Now Mr Bowman is trying to raise money online for his business making the $25 devices as well as taking orders.

“Parents can’t plan to be in the room with their child if a shooting was to happen, but they can give them an opportunity to delay the shooter long enough to run hide, or – worst-case scenario – prepare to fight,” he says on his website.

“Our goal is to provide parents a cost-efficient option to help a child barricade themselves in a room to potentially save their life and the other children in the room too.”

He came up with the idea after seeing a woman post online about giving her nieces doorstoppers for school. But Mr Bowman thought they were not secure enough.

“The Safety-Wedge will fold up under itself preventing the door from being able to continuing to go and someone from barging in,” he said.

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“Our mould we have right now is a one-cavity mould, so it can only make one at a time, but we’re looking to get up to a four-cavity mould so four can be made at a time.