Well since you know what it is in your head you should be able to draw a schematic. That's a start. It's a pretty simple device. If you can't put it into words you really don't know the material or you have a serious communication disability. Good luck.
One reactive device (a capacitor or inductor) produces one "pole." A single-pole RC filter is just a single R and a single C, wired in series. You can use it as either a low-pass or a high-pass filter, depending upon where you connect the wires to the outside world.