Quick and dirty: look at the boundary of a tubular neighborhood of a union of circles.

 circle[x_, n_: 32] := {x + Cos[#], Sin[#], 0} & /@ Range[0, 2 \[Pi], 2 \[Pi]/n];
 Graphics3D[Tube[circle[#, 72], .5] & /@ Range[-3, 3, 2], Boxed -> False]

![Image][1]

Space them approximately two units apart (using `x`) and keep their radii less than $1/2$.


 [1]: https://i.sstatic.net/h5dwv.png