If you have a credit card account, you've no doubt seen them: blank checks that may be used to make purchases, obtain cash, or transfer higher-interest balances. As it turns out, these checks are often more convenient to your creditor (for making a profit) and to thieves (for going on a spending spree at your expense) than they are to you.

When you use the checks, your creditor makes a greater profit than when you use your card. That's because:

• The interest rate on convenience check usage is often higher than the rate charged on card purchases
• The creditor may charge a substantial fee for using the check (up to 5% of the check amount, with no cap)
• There may be no grace period on purchases made with these checks; interest accrues from the moment you write one
• Your creditor may apply your payments first to balances (such as card purchases) with a lower interest rate

What's more, if you purchase defective merchandise with your credit card and you have no luck returning it to the seller, you may contact your credit card company for relief. If you use a convenience check to make the purchase, however, these protections may not apply.

Convenience checks are a favorite target of mailbox thieves. Unlike unsolicited credit card offers, you can't "opt out" of receiving them. Since you never know when the credit card company will send them, you can't report them missing when they don't arrive. Most creditors don't require a call to activate them, and merchants often don't verify signatures on convenience checks. To make matters worse, the regulations that limit your liability to $50 for use of a lost or stolen credit card do not apply to convenience checks.

So, the bottom line: It may be best to "inconvenience" yourself by using your credit card instead.