Wood veneer is sanded when it's initially applied before finishing, whenever it's refinished and anytime it gets burnt or stained. Sanding veneer is a delicate process since veneer typically consists of thin laminates. It can be especially tricky on corners and recesses of wood furniture. A gentle touch with fine grit paper will smooth and clean veneers to prepare them for finishing.
Cut a sheet of 150-grit sandpaper into strips as wide as the flat surface of a sanding block. Lay the paper on the block and slip an edge into the holding clip at one end of the block. Snap the clip into locked position to hold the paper. Stretch the strip across the sanding surface to the clip at the opposite end. Hold the paper taught while locking the clip.
Gently rub the paper over level wood veneer surfaces in the direction of the wood grain. Avoid sanding over the same spot for more than a few strokes.
Sand recessed surfaces of wood furniture by hand with a small piece of 150-grit sandpaper. Press the paper into grooves and small recesses with your fingers.
Dust off the sanded surface with a brush and rub the tack cloth over the entire sanded unit to remove all sawdust before applying the finish.
Take caution when sanding outside corners. Sand one flat surface at a time and avoid sanding toward the seam of a corner to prevent peeling veneer away from the adjoining surface.
Do not use an electric or air powered sander of any type on wood veneers. High speed vibration or rotation can sand completely through veneer quickly.