After it dried, which took about two hours, I sanded it flush with the wood using #120-grit sandpaper, then stained the entire shelf. You have to look closely to see the spot where the nail hole had been! Quick Tip: Always sand in the direction of the grain of the wood to avoid unsightly scratches.
In the picture below, the angles â ABC, â BCA and â CAB are the three interior angles of the triangle. An exterior angle is formed by extending one of the sides of the triangle; the angle between the extended side and the other side is the exterior angle. In the picture, angle â ACD is an exterior angle. Euclid's exterior angle theorem
As the picture below shows, an exterior angle (A) equals the sum of the remote interior angles. To rephrase it, the angle 'outside the triangle' (exterior angle A) equals D + C (the sum of the remote interior angles).