This design includes customizable parameters so it can be used with other plastics and printers. For printing in ABS, most of the parameters shouldn't need to be changed. Take a look at the customizer image for more info on the customizable parameters.
To assemble, insert one end of the inner clip between the hinge sections of the outer clip, and twist the other side in.
To open and close, bend the entire clip (it acts like a spring) until the inner clip has enough room to clear the end of the clip.
Support material recommended for the hinge.