By Kim Glovas

PHILADELPHIA (CBS) — Some people were hanging around in trees in Fairmount Park today, and they will probably be doing more of it all week.

They are taking part in a tree climbing class being offered by the Penn State Center: The Penn State Extension for Philadelphia.

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The students are using harnesses, ropes, knots and carabiners to get to the tops of some tall sycamores in Fairmount Park.

Certified Arborist Jim Savage says, “The idea of the class is to show people how to climb trees safely and correctly, without tree spikes, it’s all ropes and you work your way up a tree.”

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He says most of the students in the week-long class work as landscapers or arborists already, and just want to be better at their trade.

One of the first goals, hanging upside down.

“They’re gonna go probably 8-10 feet, and flip upside down, and it’s a trust thing. You have to trust what you’ve done. Ninety percent of this is what you tied is right, your belt’ll hold.

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Savage says safety is a key part of the program.