A question on Skills / Skillchecking

[Jormaine]

when the opportunity comes to skillcheck (use of perception or reading a rune) arises, does the PC in question have to have a rank in said skill or have it as a class skill to even be eligible to do said skillcheck?

EX: there is a treasure chest in a small island, and it requires you to swim across. Does said PC have to have a rank in swim to be able to swim, or can they still attempt to skillcheck on swimming?

[The floor is lava]

You can attempt almost any skill untrained, except for those few labeled on character sheets with an asterisk and it saying "trained only".

[Ross Byers]

Duplicate thread. Use this one