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.
