This summary is not the rule. The rule text controls.
If you pledge something like a promissory note, a debt someone owes you, or another type of intangible right as collateral for a loan, the person holding that pledge (called the pledgee) is the one who can sue to enforce it. In other words, if a debt gets pledged as security, the lender who holds that pledge has the legal right to go to court and collect on it, not the original owner who pledged it.
There's one exception to keep in mind. If the pledged right is actually an obligation owed by the person who made the pledge (the pledgor), the pledgee can only collect up to the amount of the debt that the pledge is securing. They can't collect more than what's actually owed on the underlying loan or debt, even if the pledged right is worth more.
This matters because it decides who has the legal standing to bring a lawsuit when a pledged asset needs to be enforced, and it limits how much the pledgee can recover in certain situations.