With the 1.3 update, a bunch of new achievements were added, including this one. Most of the (older) guides do not have crane collection for Level 15 as there were no CRANES on Level 15 previously. This guide is meant to complement those.

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The in-game achievement only requires 451 CRANES, but there are actually 452 (hence the achievement icon), so it might be easy to miss the last one.

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This is NOT a walk-through for Level 15 although the CRANES are more or less laid out along the linearity of the level.

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Kudos to the dev for sticking with this game :)

On the yellow barrel as soon as you exit from the lift.

Inside a steel locker in the room with the PC to drain pool.

This room is unmissable and required for draining pool to progress the level.

On a yellow barrel inside the first pool where you exited from the lift.

Only accessible after draining pool but unmissable as the KEYCARD next to the crane is needed to progress the level.

On the floor to the right of a heat-pipe in the room with PC above the pool with scissor lift.

This room is unmissable and required for using the security camera to find the code to open the door to the exit chair.

On the floor behind left turret in area with 3 sentry turrets and many tripwires. This area is accessible from the locked door in the room with the PC to drain pool, where the 448 cranes were found.

This area is missable. The KEY needed to unlock the door to this area is found behind a locked roll-up door in the area with the scissor lift.

And that's it! You should have all the cranes needed for the achievement!