We've all had it happen. You have a player who says, I break open the [insert container here] and get a [fairly mundane object that would reasonably be inside] from inside and then [take a clever action that you weren't expecting] so that I can [bypass an obstacle].
Some folks would break out all the rules they could and put them between the player and the goal. Do you have enough strength to break it? Make a roll. Wait, not strong enough, you use a crowbar you say, what is the strength bonus for that, and do you even have one? I'm sorry, but you can't break it. Can you pick locks? Nooooo?
By this point the player is probably pissed off. They are trying to move the story, and the game master is trying to build a wall of rules. Sometimes they have a good reason, at least for them. But we all know that there are times when it's just because they don't want to 'lose' or be 'outsmarted'.
The rules are supposed to be there to help us resolve things that might effect the story. Combat is the easiest example since it's often life and death. The rules (usually the most involved rules in the game engine) are there to simulate combat in a way that fits in with the rest of the rules. The combat rules might be exactly the same as the rest of the rules. Determine values, roll dice, rinse, lather, and repeat. They might be a whole game onto themselves that seem divorced from the rest of the game rules.
Task/Event Resolution is, in my opinion, the core of any game system. The rest of the rules are refinements or granular adjustments for that, but the core of a game engine is the resolution mechanism. If you (the GM) don't want to outright decide something or let the players run with something you should be able to comfortably fall back on the rules and the players should not feel as though you are trying to screw them when you do.
It's okay to ignore the rules to. as long as you aren't playing favorites. When Johnny tries to jump across the Chasm of Doom and you say, "Okay, you make it to the other side and keep running." that's fine. Unless you then change your tune when Boyd tries to jump across, "Roll your leaping skill." and smiling when you say it will only make it worse. If it's not important to roll to jump across the Chasm of Doom, then no one should roll, unless there is a really good reason. And not just because you don't like Boyd, or his character. Those are not good reasons. They are a sign you're not really suited to running games.