The Pen property of a canvas controls the way lines appear, including lines drawn as the outlines of shapes. Drawing a straight line is really just changing a group of pixels that lie between two points. 

The pen itself has four properties you can change:

• Color property changes the pen color.
• Width property changes the pen width.
• Style property changes the pen style.
• Mode property changes the pen mode.

The values of these properties determine how the pen changes the pixels in the line. By default, every pen starts out black, with a width of 1 pixel, a solid style, and a mode called copy that overwrites anything already on the canvas. 

You can use TPenRecall for quick saving off and restoring the properties of pens.