Originally Posted by
Yora
Okay, so any rogue, either a thief rogue or a thug rogue, can make a sneak attack against a target that did not see you at the beginning of your turn, when he has the Lurker specialization.
That's the Ambusher feat, that allows you to make a sneak attack when you begin your turn hidden, but reveal yourself before you make the attack. Like when you run out of your hiding place and cross the room to get close enough for an attack, and you are plainly visible as you close the distance.
Debatable, as it says "your skills" and the 1st playtest package was quite explicit about the fact, that this ability applies only to skills that the rogue has training in.
Which for a thief background rogue would be Find Traps, Open Locks, and Stealth. Not any other skill he might use without having special training in it.