Slotted Tenon Joints
Slotted Tenon joints are typically used as a method of fixing shelving into a unit's shelf walls. However, it can also be used for a number of other purposes.
The idea of a Slotted Tenon joint is that only one of the two pieces of wood needs to be modified in order to attain a good, tight fit. To do this, one piece has a slot made into it that is the same width as the thickness of the second piece of wood. This latter piece of wood can then be pushed into the groove, making a strong, right-angled join.
The most effective way of creating the groove (or slot) is to use a router. Although a chisel can be used, the quality of finish will not be the same (and it takes far longer to make).
Be careful when making the slot to ensure that it is not too wide, otherwise the joint will not be tight enough to work. It is far better to start with too tight a groove and widen it.
A router is not always the best tool to use however. If the groove is to hold a piece of 1/4 inch (or smaller) plywood, you should use a circular saw instead, changing the depth of cut to as little as 1/4 inch. This smaller cut is ideal when making the joint for a back panel of a cabinet, such as a bedside cabinet.