INDIANAPOLIS -- The Indianapolis Metropolitan Police Department recently warned its officers that the use of "bump keys" -- specially cut keys meant to open any basic cylinder lock, like those on home doors -- is rising worldwide.

A bump key is cut in such a way that when it enters a lock and someone strikes the key's other end -- with a screwdriver handle, for example -- it can open the lock, Call 6 for Help's Rafael Sanchez reported Tuesday.

"The bump key is just a quick way to make entry without drawing attention, without breaking glass. It's basically an old-fashioned way of picking a lock," said Jerry Cunningham, of the Danville Police Department.

Locksmiths and burglars have known about bump keys for decades, but the knowledge of them has spread on the Web.

"Bad guys used to learn this in prison. Now it's on the Internet," Cunningham said.

Many explanations and video demonstrations can be found online, and they make opening locks look simple. Purported bump keys also can be bought on the Internet.

Call 6 bought three such keys online for $23. When the keys arrived, Call 6 tried them in five different locks and had no immediate luck opening them.

"It doesn't always work," said Kelly Oliver, who works for Tinder Locksmith Service in Indianapolis. "I think it's overrated on the Internet … but it can happen."

Eventually, Brian Fultz, a locksmith with Dugan Lock and Key, got one of the bump keys to work.

Fultz said that to the untrained eye, it would be difficult to tell whether someone has used a bump key to open a lock. However, there are signs, such as indentations around the keyhole.

"The training that officers do in forensics -- this will be something that officers are going to have to look at," Cunningham said.

Experts say people can protect their home's locks. One way is to spray WD-40 into a lock. The lubrication will make the lock's pins slippery and harder for a bump key to work.

The WD-40 defense isn't foolproof, but it is the cheapest.

Another option is to get a bump-resistant lock. Most such locks require keys to make several mechanical moves inside. Look for a key with a secondary groove -- it is cut to match a specific side bar in the lock.

People also can get push-button combinations or a keycard reader with their locks.

This June, a company called Kwikset will offer a biometric lock for $200. It will scan users' finger and make sure they match with the lock's owner.

If you don't want to get new locks, you can get yours fitted to be bump-resistant by replacing the internal pins for mushroom-shaped pins, which are designed to prevent bump keys from working.

Experts say deadbolts are a must. Get one that extends at least 1 inch into the wall, they say.

Other security options include locking from the inside with sliding bolts or heavy-duty latches. If you use the lock-from-the-inside options, you can leave through a garage door.

Security Checklist From Tinder Locksmith Service

Bump Key Info -- Associated Locksmiths of America

Bump Key Info -- National Crime Prevention Council