ratlines

noun
  1. 1

    The rope or similar material used to make cross-ropes on a ship.

  2. 2

    Any of the cross ropes between the shrouds, which form a net like ropework, allowing sailors to climb up towards the top of the mast.

Source: https://en.wiktionary.org/wiki/ratline, https://en.wiktionary.org/wiki/ratlines