How about just putting a hole down the center of the highlighter for a replaceable ballpoint pen unit?

Basically, it's a clicky ballpoint pen with a highlighter marker surrounding the pen unit. Click the pen forward, and it's a pen. Retract the pen, and it's a highlighter.

This pen looks and acts like a conventional clicky pen. However, the front of the pen is a removeable cap; the cap conceals a coaxial highlighter marker around the central pen unit.

With the cap removed, clicking the mechanism switches the device between pen mode and highlighter mode.

This cap has a central hole. When fixed to the front, this hole allows the pen to poke through. When fixed to the rear, this hole allows the clicky push-button to poke through.

[edit: original description added]
-- IJK, Mar 22 2007

Highlighter with Pen Mount Highlighter_20with_20Pen_20Mount
The original inspiration [IJK, Mar 22 2007]

[+] for using the word "coaxial" with regard to a pen.
-- shapu, Mar 22 2007


your explanation was clearer (somehow) in the annotation on the linked idea.
-- po, Mar 22 2007


wot po sed
-- hippo, Mar 22 2007



random, halfbakery