Xfig 3.2.5 - An X Window System tool for drawing basic vector graphics.

Xfig is an X Window System tool for creating basic vector graphics, including bezier curves, lines, rulers and more. The resulting graphics can be saved, printed on PostScript printers or converted to a variety of other formats (e.g., X11 bitmaps, Encapsulated PostScript, LaTeX).

You should install xfig if you need a simple program to create vector graphics.