I didn't have notifications turned on for this one, but this is when I got the cheevo. During your sneaking around, you can alert the guards, - where they make a noise - but not if they see you. If they come chasing after you, the cheevo is ruined. If they think they saw something, you're ok.

The only real tricky part is at the end. Hang on the crate and look for the guard on the platform to turn away from you and start walking. When he does, book it to the shadows and then to the crate when he leaves again.