Your understanding is fairly correct, but it is mathematically easier&#x2F;nicer to tie the ends together rather than let them run to infinity. That guarantees that you describe exactly how the ends would &#x27;continue forever&#x27;, and fits better with topology.<p>See <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Knot_theory" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Knot_theory</a>