48 Modern Welding bead on the side the weld was made. Face reinforcement is the distance from the top of the weld face to the surface of the base metal. The weld toe is the point where the weld bead contacts the base metal surface. It occurs twice on each weld bead. Root reinforcement is the distance that the penetration projects from the root side of the joint. Joint penetration or weld size is the depth that a weld extends into the joint from the surface. 3.1.2 Lap Joint A lap joint is formed by two overlapping pieces of base metal. The top surface of one piece is in contact with the bottom surface of the other, as shown in Figure 3-1. Special edge preparation is not required. 3.1.3 Corner Joint A corner joint is formed by placing two pieces of base metal perpendicular or at an angle to one another so that the edge of one piece of base metal intersects the surface of the other piece near its outer edge. At least one edge of the two pieces is exposed, as illus- trated in Figure 3-4. The pieces may be joined at any angle, but they are commonly welded at a 90° angle. Corner joints may be welded as inside corners, outside corners, or a combination of both. Inside corner joints are welded along the inside of the intersection of the two pieces. Outside corner joints are welded along the outside edge of the joint. The edges may be square, beveled, J-grooved, fl ared, or edge-fl anged. See Figure 3-4. 3.1.4 T-Joint A T-joint is formed by two pieces of base metal that are at an angle of approximately 90° to one another. The main difference between a corner joint and T-joint is that a corner joint is formed along the edges of both pieces, while a T-joint is formed at the edge of one piece and away from the edge of the second piece. The edges of the base metal may be prepared as a square, bevel-grooved, J-grooved, or fl are-bevel-groove joint, as shown in Figure 3-5. Both edges of the base metal may be prepared to form a double-bevel-groove joint. Fillet weld on an inside corner (no preparation) Square-groove weld on an outside corner (no preparation) V-groove outside corner Bevel-groove outside corner J-groove inside corner J-groove outside corner U-groove outside corner Bevel-groove inside corner Single-flare-bevel-groove weld on an inside corner Single-flare-bevel groove weld on an outside corner Edge weld on a flanged corner Figure 3-4. Various methods of preparing the edges of corner joints. Three of these joints require the base metal to be bent for proper formation. The fi rst two corner joints depict no special preparation of the edges.