Call of Duty WW2 (COD WW2) contains a secret Pack-a-Punch easter egg on the Groesten Haus map. This guide shows you how to unlock the pack a punch mystery box.
Step 1 (Unlock Mystery Box): Shoot the 10 lanterns around the map. 4 are downstairs, 2 are outside the downstairs windows, 4 are upstairs. They make a raven sound when you shoot them and start glowing purple. This unlocks a secret room upstairs that contains the mystery box.
See the screenshots below for the raven lanterns (or check the video above):
Step 2: Draw a Jack-in-the-Box from the Mystery Box. This is random but it’s always one of the first few things you draw. Usually within the first 5 draws, but guaranteed within the first 10 draws.
Now throw that Jack-in-the-Box on the wooden beam outside the mystery box room, at the end of the wooden beam where the staircase starts. See the screenshot below or check the video at the start of the page if you’re unsure.
Step 3: Collect 10,000 points by killing zombies. Then interact with the Piano in front of the mystery box room (upstairs) to pay 10,000 points. On PS4: hold 
/ on XB1: hold 
.
Now everything you draw from the Mystery Box will be pack-a-punched automatically! Unlike other maps there’s no actual pack-a-punch machine. Instead, all weapon draws are immedately pack-a-punched. The best part: they continue to cost only 1000 points per box draw. By collecting “Max Ammo” pickups you can restore all your ammo.
That’s the whole Pack-a-Punch easter egg. It will likely take you until round 8 to complete it.
This only works on the Gröesten Haus map (solo and co-op). It does NOT work in the Prologue!
By some reason the pack a punch didnt unlock for me, even though i did exactly as you showed.
Could still not use the piano.
Are you doing it in Groesten Haus map?
It does not work in Prologue. Maybe try throwing another jack-in-the-box up there again.
sane problem here….sometimes i do succeed i think throwing jack on the beam is not enough it needs to be on the correct spot…or else i dont have an explenation for why piano doesnt accept 10k
It does not say to pay 10000 but if you hold done square on ps4 and x on Xbox it should still work.
How do I angle my jack-in-box for it to land on the beam?
Use the video guide and practice