Homemade Power Jelq
The "Power Jelq" or "Jelq Device" is a commercial jelqing device using the Jelq Stick principal. It retails for $60, and this is a make at home equivalent for $10 using the same style of canning tongs used on the commercial device, the only difference being the type of foam and the use of plastic rather than metal inner rollers.
The rollers shouldn't rotate in use.
Like the commercial version, the tongs will start to degrade at the pivots after a time and this increases the chances that an arm will detach from a roller. As the arms are sharp metal and the penis is somewhat softer, protecting the end of the arm is a sensible precaution.
This design is simple and quick to construct without the need for tools beyond a sharp knife.