Q. My neighbor cut down a tree on his own property, which is OK with me because the tree was a real "weed tree." The trunk, about 12 inches in diameter, sticks up about 5 inches. My concern is that the stump might produce a few more saplings, starting the cycle all over again. How can that stump be killed?

- Charlie Dellanno, Somerville, Mass.

A. Maples tend to grow saplings out of the stump, and so might Ailanthus, the tree of heaven, which is termed a city tree by some, a weed tree by others.

Whether or not saplings might grow, you can kill the stump by drilling holes in the trunk and filling them with salt and adding water. Add more salt as the salt dissolves. Or, have a tree specialist grind the stump out, removing it entirely.

Q. I am filling in holes in the floor where a heating vent was removed, using yellow hard pine boards to match the original flooring. Trouble is, the old flooring is 3 1/4 inches wide, and I can only find boards 31/8 inches wide. What can I do?

- Stan Pittman, Shelburne, Mass.

A. You may have to have some boards custom-made. At any rate, call or write to the Southern Forest Products Assn., PO Box 641700, Kenner, LA 70064-1700, 504-443-4464. The association could tell you if it sells 31/4-inch boards, tell you where they can be found, or custom-make a few boards. You might find a cabinetmaker who could mill wider boards down to the right size.

Another trick might be to take up some of the old boards out of a closet or other inconspicuous spot, and use those. You can fill in the closet boards with almost anything.

Q. I read your story about oil tanks and leaks and other problems. I have to replace my oil-fired house heater, and am wondering if now is a good time to stay with oil or switch to gas. What are the advantages of each?

- Debby Harrington, Charlestown, Mass.

A. The ony advantage to switching to gas, in my opinion, is getting rid of the oil tank in the cellar, which is not only an eyesore but a space-taker as well. But, also in my opinion, this is no reason to switch, mainly because gas fuel is more expensive than oil.

Q. I am replacing the shingles on my garage roof, which is a hip roof, with slopes going down all four sides from a point. Is it necessary to ventilate the garage? I also have an old picket fence that has been stored for some time in the garage. It looks good, and is sound. Is there any reason I should not install it now?

- Jim, from Brighton, Mass.

A. First, the fence: Go ahead and install it. It will give you good service. Be sure to use hot-dipped galvanized, stainless steel, or brass fasteners to resist rust.

OK, the roof: The garage does not have to be ventilated except to keep it cool in summer. Opening windows will accomplish that, except heat will rise into the ceiling, trapping hot air. A cupola on the point of the roof would let a lot of that air out and will be decorative, too.

Q. I stripped the paint off the exterior wood pillars on my house; the wood is really dry. Should I treat them with oil before painting? Also, some of my floors are sagging. Who should I contact to fix them?

- Paula Lovejoy, Cambridge, Mass.

A. You don't need oil to treat the pillars before painting; the idea of "feeding" dry wood is an old wives' tale. Wood is supposed to be dry. It would be OK to treat the pillars with oil before painting, which would allow the paint to adhere better. But it would be better not to paint, but to treat the pillars with two thin coats of a latex solid stain. Such a stain will resist peeling and will be good for five years. As for the professional to check your floors, find a carpenter who is familiar with old houses and who can determine what is causing the sagging and fix it, or at least stabilize the floor to keep it from sagging further. The joists may not be big enough, or the center beam is dropping a bit. There are other reasons for sagging or slanting floors, but most of them can be corrected.

Q. The tenants just left the rental unit of my two-family house, and I discovered several ropes broken in the windows. Who should I contact to fix them? One man suggested that I use chains instead of ropes when I replace them. Is this correct? Can any insulation be put in the space where the weights go up and down?

- E.S., Brighton, Mass.

A. Find a handyman or carpenter, but the man who suggested you use chains instead of ropes has a point because chains will last longer than ropes; in fact, indefinitely. Be sure to get solid brass sash chain. Those weighted windows are the best you can get, in my opinion, because there are no springs to fail. One disadvantage is that you cannot fill the weight pockets with insulation because that would render the weights inoperable. The small loss of heat through the weigh pockets is compensated by the quality of the windows.