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When it comes to terminology in repair procedures, there is often a great deal of confusion as to what type of sectioning joint is called out in a specific repair procedure. To help end some of that confusion, let's look at the three basic sectioning joints.
An open butt joint joins two pieces of metal that are parallel with each other and butted against each other. Some vehicle makers such as Honda will refer to "cut and join" in the repair procedure. This is the terminology they use for an open butt joint. Often times, open butt joints may be offset from each other, like on a front lower rail where the inner and outer rails are cut at two different locations.
A butt joint with backing joins two pieces nearly butted against each other with a backing piece that is usually the same thickness as the other two pieces. This type of joint requires a gap of about two to three metal thicknesses between the two butted pieces.
Lastly is the lap joint, which uses a fillet weld. A fillet weld is roughly a triangular bead deposited in a corner formed by the fit-up of two pieces of metal. This type of weld may also be called an overlap weld or a lap weld. When used for sectioning joints, a fillet weld is made on two pieces of metal that overlap each other (one on top and one on the bottom).
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Article validated in 2025