You get them professionally cleaned time to time which works fine, except you notice edges getting darker and darker that doesn't get clean when the carpet guy comes. The problem is dirt getting into your carpets from below, through tiny cracks and open seams under your carpets where walls meet floors and on stairs. Over the years air passing through leaves dirt on your carpet like a filter. Next time you carpet, seal all open cracks and seams with a good bead of caulk before new carpet is installed to keep it looking great. There are two types of nails, common nails and finishing nails.
Common nails have large flat heads and are for rough work.
You can gauge how long a nail is by dividing size by four and adding a half-inch. An eight-penny nail would be eight divided by four plus one half inch to make it two and one half inches long. To always get the best price buy in bulk. Use a whetstone as an abrasive surface. Just wet it with a little water.