Stud finders don't actually find studs. They find changes in reflected (inaudible) sound waves. So, there is something there that is more dense than the sheetrock (or whatever) you have over it. Could be pipes (probably not unless you're drilling into a "wet" wall, usually reserved for behind toilets/showers/tubs), could be you've got metal or metallic studs (some construction, especially high-volume housing), could be wires just in the exact place you're scanning. Try scanning above and below by about a foot. If you're still getting a metal return, you might want to consider relocating your project.