Before anyone tries paycheck parking, I think they should meet its simpler cousin: the biweekly payment. It's the rare money trick that works exactly as advertised, and for some households it's the better fit.
The mechanics take one sentence. Pay half your mortgage payment every two weeks instead of the full payment monthly, and because the year holds twenty-six half-payments, you make thirteen full payments instead of twelve without ever feeling the extra one. That thirteenth payment goes straight to principal, year after year. On a typical thirty-year loan, the habit shaves several years off the term and a serious pile of interest. No line of credit, no applications, nothing to manage. If your lender doesn't offer a true biweekly plan, you can copy it yourself by adding one-twelfth of the payment to each month, aimed at principal.
So how does it stack up against parking? Parking is the more powerful machine. Every dollar of your income fights interest on every single day it sits in the line, and chunks hit principal far harder than one extra payment a year. But that power arrives with moving parts: a line to qualify for, a surplus to verify, habits to keep, and failure modes if the habits slip. Biweekly payments have no failure mode. They're a ratchet. Set them and they only turn one direction.
Here's how I'd choose. If your real monthly surplus is thin, your income is unpredictable, or you know a spending plan won't survive contact with your household, take the biweekly plan and be glad. It captures a real share of the benefit for none of the risk. If your surplus is strong and your bookkeeping is honest, parking does more work. And the two aren't rivals anyway. Plenty of people run biweekly-style discipline on the mortgage while the line handles other debts. See when chunking is the wrong move for that split.