In the case of relieving angles, the typical shim requirements used are almost always require a single slotted. The stock version of this is 3” wide.
While shimming moment connections single slot steel shims can be used in the above example, most often the fabricator requests multiple slotted steel shims designed exactly for the connection. The left side of the column in the photo to the left shows a standard moment connection before the beam is attached. The contact surface of each moment plate is 6” wide x 10” long. That said, those dimensions do not include the section of the moment plate that extends inward from the edge of the column flange toward the web.
To shim this kind of connection using only one-piece shims, the fabricator will use two shims, both 3” x 10”. They will be inserted from each side, meeting in the middle. An example of these two shims is shown below.
This method is faster and leaves a solid contact surface around all edges. No gaps will be visible from either side.
Single slotted shims are produced on what is known as “hard tooling.” This means that the tooling is inflexible, so it makes one part, and only that part.
To see The Steel Supply 
Company stock single shim catalog, click here. With proper hard tool maintenance, this system will produce exact shims with absolutely no compromise in the surface.
To manufacture multiple slotted shims like the drawing on the left, The Steel Supply Company uses a variety of cutting methods, all of which are “soft tooling.” This is different from hard tooling, because in this case, the tooling can be adjusted to different shapes and configurations. With moment connections especially, it is essential that the shim be perfectly flat and be free of any “roll” where the steel was burned and misshapen. The “roll,” known as dross, is common with high definition plasma systems. If dross is apparent, it needs to be sanded or ground off so as not to create an uneven edges.
