Make a flat hand-sanding block

Choose a block suited to the surface

A sanding block supports abrasive so pressure is spread more evenly than it is under fingertips alone. For flat surfaces, begin with a flat, rigid block. Soft backing can be useful for some tasks, but it also makes it easier to round edges unintentionally.

A comfortable first size is 120 × 65 × 25 mm. Use sound wood without knots at the gripping edges. The exact dimensions can be adjusted to your hand and abrasive sheet size. Check that the block is large enough to grip without fingers rubbing the work.

• Block: approximately 120 × 65 × 25 mm.
• Abrasive paper sized to wrap over both short ends.
• Optional thin cork backing, only if the intended task benefits from slight cushioning.
• A straightedge for checking the working face.

Preserve a truly flat working face

Mark one broad face as the sole. Check it with a straightedge in both directions and diagonally. Correct obvious high areas using a controlled method, then recheck. Do not assume a factory-sawn scrap is flat enough simply because it looks smooth.

Ease the upper gripping edges generously, but leave the sole’s perimeter only lightly softened. A heavily rounded sole edge reduces support near the edge of a board. If adding cork, use a uniform layer and compatible adhesive, then ensure there are no bubbles or thick glue ridges.

Fit the abrasive securely

Cut the paper long enough to cover the sole and fold over both short ends. Hold those folded ends above the working face during use, or use a simple external holding method that cannot scratch the work. Keep staples and exposed metal away from the sole.

The paper should lie taut without a wrinkle beneath the block. A wrinkle creates a concentrated ridge of abrasion and can leave marks. Replace paper that is torn, clogged, or detached rather than compensating with more pressure. Keep different grits labeled so a coarse sheet is not mistaken for a finishing grit.

Use the block with feedback

Practice on scrap, following the grain where appropriate and keeping the block level. Use light, even pressure and inspect frequently in raking light. A pencil grid can show where abrasion is occurring, but remove it without sanding much deeper than necessary.

Secure the workpiece so it cannot skate away. Collect dust and use protection appropriate to the material and task. Avoid sanding unknown coatings. Store the block with its sole protected from dents; a small bump trapped under the abrasive can transfer into the work surface.