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This article is about the woodworking joint. For the machine element, see Spline (mechanical).
A spline joint can be viewed as an extended biscuit. Two boards have extended, matching grooves lined up and facing each other. The void between is filled with a thin piece of wood, forming a spline joint. This is very similar to tongue and groove. The difference is that the spline essentially forms a tongue, a 'loose tongue', for both grooves. It is often joined with glue.
