| After looking at examples of spline joints I'm even more confused. Which
| direction is the spline supposed to go in? If looking at a miter joint,
| say, in a box, does the spline go in from the top of the box "down", or from
| the side of the box "in"?
| For example, look at the splines on these two pages:
| It would seem to me a biscuit would be more like the spline in the first
| photo? Is this what I need for this application?
The first site illustrates how to do a spline if one does not want it to show. Lots of glued strength results.
The second site illustrates how to do a spline if one also wants the spline to be decorative. The splines can be straight cuts as shown here or bowties or whatevere seems aesthetically pleasing. One can put in as many as seem appropriate to the construct.
Either way works.