By the way, is that the ARB hydraulic jack? If so, they really don't want you to keep it on its side. Whenever you need it, you'll likely need to pump the handle for a while to get all the air from the lines.
I understand that to be a longstanding misconception (primarily in the US, it emerged on Jeep forums). I had the same question following initial research and had a chat to ARB when I purchased it, who indicated this is incorrect and that they store stock on its side in both the warehouse and retail outlet. It is however not to be
operated in a horizontal position.
Here are the storage instructions from ARB:
STORAGE
Store Jack with the shaft fully retracted (Jack lowered), the handle retained in the rubber bumper and the hook in the upright position.
Ensure the Pressure Relief Button is not depressed while in storage. Storage with Pressure Relief Button depressed may cause oil leakage.
When not in use, the Jack should be stored within the supplied carry bag.
If the Jack is transported within a vehicle, ensure the Jack is adequately restrained so as to not become a projectile in the event of a collision.
That said, if the oil seals are compromised OR the Pressure Relief Button is depressed it will lose oil when in a horizontal position (but not in the vertical - note the storage instructions are presuming it’s on its side), hence it’s important to periodically remove and inspect/test it as mentioned earlier. The other method is to store it in it’s original plastic sleeve, in which case any oil leakage is immediately visible (and contained).
In Australia they are most often kept in the bag and carried in (tossed into) the loadspace or tub, no problem. Thank you for the heads up though, I very much appreciate the good intentions!