NFL's clegg hammer impact tester

JACKSONVILLE, Fla. – Grounds crews across the NFL are responsible for way more than making sure the playing surfaces are measured correctly and look pristine. The process for getting a field ready for Sunday also includes using a Clegg Gmax 2.25-kilogram hammer.

The instrument is used to determine the hardness of the playing surface prior to the start of each game. The hammer is dropped from a predetermined height to measure how quickly weight stops upon impact. According to NFL rules the reading must produce a score under 100 before a game can be played.

The higher the number the harder the playing surface. In turn that also means there's a higher risk for a player to suffer a concussion if his head hits the ground. EverBank stadium assistant sports field manager Nick Fedewa walked the Channel 4 sports team through the process.