In the world of air miles and hotel points, the buck stops at Delta SkyMiles -- meaning that once you've converted your Marriott Points or other rewards program points to Delta SkyMiles, there's no converting them to a credit in any other program. But before you fling up your hands in frustration, know that there is still a way to use your SkyMiles for a hotel stay at a Marriott hotel; you just have to use those miles to book a room directly with Delta.

1. Login into Delta SkyMiles Marketplace

Navigate to the Delta SkyMiles Marketplace web page and log in at the top of the page using your SkyMiles number, PIN and last name.

2. Click Book a Hotel/Rent a Car

Click "Book a Hotel/Rent a Car" from the left-hand sidebar menu.

3. Enter your travel information

Click the hotel tab on the reservations box that appears, then select your desired location, dates of stay and number of people in your party, then click "Search."

4. Find the Marriott hotel that works for you

Scroll through the list of available hotels that appear on the results page. When you find the Marriott hotel that works for you, click "Continue" next to its description.

5. Select Your Room

Select the room type you would like at the next page, then click "Continue."

6. Review the miles need for the hotel

Review the number of miles needed for the hotel (and the remaining dollar amount you must pay if you don't have enough miles for the whole hotel) and click "Continue."

7. Finish your Reservation

Enter your name, address, email and other necessary personal information at the next screen, and follow the remaining prompts to book the reservation. If you need to pay a remaining dollar amount to book the room, enter in your credit-card information when prompted. Be sure to write down the confirmation number for your reservation, or print the page when it comes available on the screen.