The crossed-lines method of constructing <a href="https://en.wikipedia.org/wiki/Curve_of_constant_width" class="extiw" title="en:Curve of constant width">curves of constant width</a> (blue) from an arrangement of lines (black). The circles whose arcs form the boundary of the curve form nested pairs, with the inner circle shown in dark red and the outer circle shown in light red.
<a href="//commons.wikimedia.org/wiki/User:David_Eppstein" class="mw-redirect" title="User:David Eppstein">David Eppstein</a>
<span class="int-own-work" lang="en">Own work</span>