Ratlines....
are for feet, not hands
because there is no chance someone will step on your fingers that way.
Always hold the shrouds.
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Lines or chains....
may feel solid sometimes, but they can move without warning.
No running rigging is safe to hold or step onto
Avoid them as foot holds or hand holds.
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Apart from ratlines and chains, which are black but not safe to hold, as a general rule,
if it's black it's OK,
if it's brown it's likely to move, so avoid holding onto it. 