Some days - particularly when rain or the temperature falls - it does seem rather a waste of time to go out for lunch. So invite lunch in. A phone call will bring even a single sandwich to your desk if you're in the right neighborhood.

That is downtown, between 10th and 17th Streets from Constitution Avenue to K Street, you are in luck. Loeb's Restaurant will deliver free from 8 a.m. to about 3 p.m., as long as your order includes a sandwich. It is likely to be a hearty sandwich, heavy on the pastrami or roast beef or whatever. The newest, called La Scala, $1.75, is a kind of Italian sloppy joe on French bread, said to have come from somebody's old country heirloom recipe. On a cold day, their soups are worth investigating. Or, if the day is really dreary, treat yourself to their homemade brownies and cookies.

You could easily have a wine and cheese luncheon party - if you are in downtown Alexandria. The new La Cheeserie will deliver anything from a pate sandwich to a whole cheese platter. Sandwiches range from $1.20 for Swiss Emmenthaler to $2.19 for smoked salmon and cream cheese. Or you could order quiches ($1.10 to $1.35), salads, or just the cheese of your choice. Sandwiches are large, the pate particularly recommended. And they will send along wine, from a tiny eighty-five-cent bottle of Almaden on up to something very grand. Deliveries are made all day from Monday to Saturday, but never on Sunday.

Loeb's Restarant, 617 15th St. NW. Deliveries Monday through Friday 8 a.m. to about 3 p.m. 783-9306.

La Cheeserie of Alexandria. Deliveries Monday through Saturday 9 a.m. to 6:30 p.m. Open (but no deliveries) Sunday noon to 5 p.m. 548-6560 .