Which skill check (if any) lets characters free themselves from rope bindings?

Question

The characters will find themselves tied up to trees. What skill check will they need to use - Athletics?

Answer 1

Escaping is an Acrobatics check.

Set the DC according to the difficulty of escaping from the bonds (set the difficulty as easy/hard/medium and give it a level, then go the the DC table and see what it should be).

Depending on how you've tied up your PCs, athletics may also be appropriate (see Escape section linked and quoted below). Generally though Acrobatics is preferred here.

If you would like you can set one skill as the easy or medium (wriggling from the bonds is easier than breaking them or some such) and one as medium or hard to give some consequence as to how your PCs choose to escape.

From Acrobatics:

ESCAPE FROM RESTRAINTS Make an Acrobatics check to slip free of physical restraints such as manacles.

Action: The check takes 5 minutes of uninterrupted effort. Alternatively, a creature can make the check as a standard action, but doing so increases the DC by 5. DC: Hard DC of the creature's level.
Success: The creature slips free of the restraint.
Failure: The creature can try again only if someone else provides assistance, most often by using the aid another action.

From Escape

Escape a Grab or Immobilizing Effect
Action: Move action.
Acrobatics or Athletics Check: The creature makes either an Acrobatics or an Athletics check. Normally, the immobilizing effect specifies the DC for the check. If no DC is specified, an Acrobatics check is opposed by the Reflex of the immobilizing creature or effect, and an Athletics check is opposed by its Fortitude.
...
Success: If the check succeeds, the immobilizing effect ends on the creature, which can then shift 1 square.

Something else to consider, if this is an out of combat scenario, you almost certainly want to work this out as a skill challenge. Design it so that athletics, acrobatics, and perhaps thievery are primary stats, and things like perception, endurance and another skill are secondary things.