A 7 × 10 rectangular box, packed with 2 × 5 rectangular bricks by subdividing the box into smaller 5 × 10 and 2 × 10 rectangles, each of which can be tiled by translates of the brick. The 2 × 5 brick is not harmonic (its sides are not multiples of each other) so, according to <a href="https://en.wikipedia.org/wiki/De_Bruijn%27s_theorem" class="extiw" title="w:De Bruijn's theorem">De Bruijn's theorem</a>, they can be packed into at least one box that is not a multiple of the brick.
<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>