Anytime you need to span a distance longer than the lumber you have on hand, scarf joints are a good solution. This stop bladed scarf joint with pegs is a variation on the scarf joint. It is really a half-lap joint with stops, also called tongues or blades. The stops improve bending and tensile strength and help prevent twisting.
All joints need to be further secured in some way. In this case, we use hardwood pegs inserted vertically to hold everything together. They make the stop bladed scarf joint with pegs a great solution for a sill or roof plate.
I have used this joint, and love it—easy to cut, but with tapered pegs and slightly offset holes, it’s incredible strong. A 28′ beam with this joint in the middle shows no bend at all when lifted by its ends.
But I don’t understand the term “stopped” in the name.
The stops, also called tongues or blades, are the extra cut out in the joint forming a 90-degree surface. The stops improve bending and tensile strength and help prevent twisting.