SEOUL — The sound of hammers and saws and the smell of paint and plaster fill the air as men of the 6146th Air Force Advisory Group work to build a permanent home, for 77 children of the Sungnam Orphanage.

The orphanage south of the Han River bridge is rapidly taking shape with the twice-weekly visits of Americans from Seoul International Airport.

Concrete floors and painted sidings are being installed in preparation for the cold winter months ahead. There is a school next door for the children and the Republic of Korea government supplies the necessities. But what goes to make a house a home is supervised by Mrs. Annie D. Ruff.

"The kids just live for our visit, and I live to visit them," she said.

Happily surrounded by children, Mrs. Ruff combines the ordinary distaff talents of cooking, mending and house cleaning with the more hardy endeavors of plastering, painting and carpentering.

"Of all the welfare work I've done," she says, "this has been the most enjoyable because it's appreciated in a manner only you could tell."

Her husband, Lt. Col. Fred J. Ruff, engineer of the advisory group, is chairman of the orphanage but gives all the credit to his wife.

"She took the place over and though we've only been working on the building for a. month now, we've gotten as far as we did because of her," he said.

Telephone callers to the Ruff household usually hear, "Good afternoon, Ruff residence, Orphan Annie speaking." Mrs. Ruff, according to those associated, with her, takes the orphanage very seriously.

Chaplain (Maj.) William H. Biggs says that the "combined effort of Mrs. Ruff and the other wives, with that of officers and enlisted men, has really gone into this thing to make it come along as quickly as it has."

"We started this orphanage from the ground up and we're working hard towards a real Christmas for the kids," Chaplain Biggs said as he waved a paint brush.

A 10-year veteran of the Far East, Mrs. Ruff feels she "knows the needs and understands the people over here. And, of course, I love them," she said.

Besides the touches of home, the pictures on the wall, the curtains on the windows and mats on the floor, the children are aided in their homework by the donation of a giant abacus, or chu-pan, the Oriental computer, and 20 smaller ones for the children to practice on.

"We don't want to overlook anything," says Mrs. Ruff.

Enlisted men have contributed to the project by hefting brushes and hammers and using their off-duty hours to join in the project.