Sharp angles caused by the meeting of surfaces in different planes should be avoided in solid metal work wherever possible. A sudden change in the direction of a surface, causing a sharp angle as at B, Fig. 112, is detrimental to the strength of a casting or forging in the angle. This condition may be avoided by making the change of direction gradual, as at C. In shop parlance, the corner C is said to be filleted.

Pattern shops are supplied with a soft metal fillet material wound on reels. This is tacked in all angles of patterns where fillets are not made in the wood itself in the course of shaping it for the pattern.