Q: we stripped the old finish from our oak dining-room floor and are ready to refinish it. Here are some of the problems we face: There are cracks up to 3/8" wide between some of the boards; can we fill them with wood putty? We're thinking of using a penetrating sealer to refinish the floor. Do we need to put polyurethane on top of that? And how do we wash the refinished floor? A: First, the bad news. Since the wood in floors constantly shrinks and expands as its moisture content changes, it's vertually impossible to make a lasting repair of cracks between boards with wood putty or later work loose and come out. It's possible that some of the cracks will disappear this summer, when the wood will absorb some moisture and expand. If there are only a few very wide cracks, I suggest you remove those boards and install new flooring at those points.

Otherwise, you'll probably have to learn to live with the cracks and cover the worst of them with furniture and area rugs.

I have good news about penetrating sealers, also called penetrating resins. Sealers such as Tungseal, Watco Wood Floor Finish and Dura Seal give a complete finish favored by many floor experts.

This is what the National Oak Flooring Manufactures Association says about penetrating sealers: "This is the finish recommended for most residential floors. The sealer soaks into the wood pores and hardens the floor against dirt and most stains. It wears only as the wood wears and will not chip or scratch. After years of wear the floor can usually be refinished without sanding by cleaning it and applying another coat of sealer . . . Limited areas of wear can be refinished without showing lap marks where the new finish is applied over the old."

In short, you don't need polyurethane if you use the proper type of sealer (read the directions on the can carefully), although polyurethane varnish is a good topcoat for wood floors subject to high traffic, spills and stains.

How is a wood floor washed? It isn't, or at least it shouldn't be. Never use water or even a water-based cleaner on a wood floor. Give the floor a coat of a buffable wax and vacuum it frequently. If the floor becomes dull, buff it, and if it becomes dirty, clean it with a solvent-based cleaner-wax. Q: Some of our ceiling tiles became discolored because of a leak in the roof. After the leak was fixed I painted the tiles, but the stains showed through. Even a second coat of paint didn't cover the marks. What do I do now? A: Water stains, knots, oily spots, rust and some other stains will bleed through paint unless they're sealed before paint is applied. A coat of shellac will seal many stains, or you can use a shellac-based primer-sealer such as b-i-n or Gripz. Q: How do I repair a broken window pane in a metal frame ? A: If you look closely at the corners of the frame, you should see fine lines showing where the mitered corners of the frame fit together. The corners are held together by clips. If the frame has a channeled edge, the clips will be visible and can be pried out with a screwdriver. In other frames, the clips are inside the frame and the mitered joint must be carefully pried and pulled apart.

While it's possible for a do-it-yourselfer to repair metal-framed storm windows, it's usually best to let an expert handle the job.

If you repair the windows yourself, you should use acrylic plastic safety glazing instead of glass if the sash is part of a door or in a hazardous location. You might also need to replace the rubber gasket that fits inside the frame. The gasket should be glued in place with clear cement or silicone adhesive sealant. Q: Where can I find a pattern for a fancy trellis or arbor of the type used to support vines ? A: Check in the house and garden section of your local library first -- it may have what you need right on its shelves. You'll also find some excellent ideas in "Sunset Garden & Patio Building Book," one of the Sunset Books sold at many bookstores, home centers, garden-supply stores and even some supermarkets. If you can't find a copy, the book can be ordered directly from Lane Magazine & Book Co., Menlo Park. California 94025.