Sharpening scrapers

Cabinet scrapers aren't usually included in the modern toolbox, but they work very well for smoothing surfaces--better than sandpaper--and I highly recommend them.

A simple thin, flat piece of steel will work for scraping, but if the edges are sharpened and burnished correctly, it is much more effective. Some woodworkers have developed specialized scraper sharpenings for different work, but just the basics will get you pretty far along.

New cabinet scrapers usually come unsharpened, and should be sharpened before the first use.

There is a good article here on how to sharpen and shape a scraper.  (And an even better one here, with pictures.) The basic idea is that you make the edge of the scraper perpendicular (or square) to the sides, and then put pressure on the edge of each side (using a burnisher--a piece of smooth steel that is of harder steel than the scraper, such as a tool made of tool steel) to make the steel overhang the scraper's edge by a tiny bit:  "raising a burr". Then use the burnisher again to bend the burr back toward the side. The end result should be that there is a tiny, continuous blade of sharpened steel all around the scraper (and perpendicular to its surface). This is what does the cutting when the scraper is used.

When I sharpened my scrapers, I didn't use blocks or jigs, but did it all freehand. It took some fiddling to figure out how to position my hands and the scraper and the burnisher to make the metal go how I wanted, but eventually I got there.

The first article also pointed out some interesting things about how burnishing actually hardens the steel of the scraper and makes the cutting edge last longer.