Twist pens are extended and retracted by twisting part of the body or cap. Twist pens oftentimes have slimmer profiles, but not always. These are usually refilled by pulling the two sides of the pen apart.

Pictured: Blue Resin and Maple Wood Twist Pen with Chrome Plating.

Click pens are extended and retracted by -you guessed it- clicking them. Click mechanisms can be soft or stiff, loud or quiet, depending on the pen. Some click pens feature an all-metal internal click mechanism for enhanced durability.

Pictured: Maple and Wenge Wood Segmented click pen with gold and gunmetal plating

A postable pen is just a fancy way of saying it has a cap that can mount on the back of the pen while it’s in use. So, the action for this pen would be to just uncap it, and stick the cap on the back or lay it on your desk.

Postable options are most often seen with fountain pens, rollerball pens, or rollerball pens that can be converted to fountain pens. This is typically a feature on a larger-bodied pen.

Pictured: Buckeye Burl Wood Postable Rollerball Pen with Chrome Plating

Fountain pens are used by filling an ink reservoir in the body of the pen. The ink then flows down to the tip. Inks can be just about any color. Nibs (the writing tip of the pen) come in several sizes, are replaceable, and some pens can be converted to rollerball with additional parts. Fountain pens are typically larger pens.

Pictured: Australian Mallee Burl Wood Fountain Pen with Black Titanium Plating and #5 Nib

Bolt action pens are extended and retracted by a “bolt” on the top side of the pen. Bolt action pens are not limited to gun-themed pens; they make their appearance on a wide variety of hardware. Bolt actions pens are typically “stiff” to actuate, but very satisfying. Keep in mind, if you are left-handed, many (but not all) bolt action pens are only configurable for right-handed users.

Pictured: Ziricote wood semi-automatic bolt action pen.