Snap joints are common mechanisms for linking two extrusions. When designing a snap joint, there are a number of things to bear in mind. The design of a joint varies depending on whether or not it is to be opened.
The movement of the snap element must fall within the elastic range. Snap locks with a plastic deformation are very rarely the best solution. In general, long snap lock lengths require a snap movement of only a few tenths of a millimetre. Double snap locks are usually not necessary. One frequently-used solution involves one extrusion rotating in some form of joint.
Using the figure below, you can establish the required shank length when designing a snap as a function of snap height and material thickness.
Example of a snap joint
The above figures show examples of different types of snap joint. If the material is not flexible, other solutions may be used. The example below illustrates solutions where a rubber extrusion (left) and a steel clip is used as the springing element.