http://deltaschooloftrades.com/basic_joints.htmWorth a look
The T joint and fillet weld are the most frequently used joint and type of weld.
In the same way the edges of the butt joint may be prepared for welding, the tee joint’s vertical piece may be prepared using a Bevel, or J shape. The preparation allows the Welder to penetrate into the root of the joint.
See examples below:
