For most men it's hammering your first nail, completing your first oil change, or even surviving that first – and hopefully only – bucks night.
But for someone as big and as young as David Klemmer, someone who is still learning the ropes in his rookie season, standing up to one of the game's premier props in Jared Waerea-Hargreaves was the ultimate rite of passage.
After all, nothing earns you more respect in the land of giants than going toe-to-toe with arguably the meanest giant of them all.
"Exactly, that's right," Klemmer nodded on Tuesday. "Me and Jared went at it and he's a good player I respect."
The rugby league world winced in unison when the young bull came off the bench and singled out the old one deep in the throngs of ANZ Stadium. The crowd hushed as he called out the Roosters spearhead, and the couch potatoes sat up when they began to lock horns.
Even some of Klemmer's teammates admitted to raising an eyebrow when the young fella grabbed Waerea-Hargreaves by the shirt and egged him on.
"I wouldn't expect Klemmer to take a backwards step, but there's probably smarter blokes he could run at," fellow Bulldogs prop James Graham half-joked this week.
"His choice of target wasn't the smartest, but that's Klemmer. And good on him."
The Toongabbie junior – yet another Eels kid who has blossomed outside of Parramatta – had played just 10 games for the Bulldogs this year before the clash with the Roosters.
But as he was handed the interchange card to come off the bench that night, the rookie felt he had seen enough to know that things weren't quite going to the same script that had propelled the Bulldogs to a seven-game winning streak.
"As the game went on, we needed to tip them over. They were going through us a bit. [So] me and Sammy Kasiano thought we'd try and change the game around," he reasoned.
"[But] I knew once I started, I couldn't back down. I couldn't just hide somewhere, I had to go on with it. And I loved it."
Not unlike their grand final run in 2012, the Bulldogs have risen as the cream of the NRL this year on the back of a skilled forward pack that boasts an engine like no other.
Their starting front row of Aidan Tolman and James Graham chew through more yards than a herd of cows on steroids, their Country Origin duo of Josh Jackson and Dale Finucane fit a week's worth of work into a simple 80 minutes, and on the edge they've got man-eating dinosaur Tony Williams who has finally found his way from the ice age.
But in David Klemmer, coach Des Hasler might have just found himself a bona fide enforcer. A six-foot-six big man that opposition players can barely see eye-to-eye, let alone try to match chest-to-chest.
And after his encounter with a bloke who does that for a living, someone who has won a premiership doing so, Klemmer heads into Friday's blockbuster against Manly having learnt the biggest lesson of his career.
"If it's in the game, I would be in there. If it's not, then I just play my game. If it happens, it happens," he said.