Here is one form yesterday, newer panel, installed sideways, open knockouts, pointed screws, and oh it’s installed in a basement bathroom next to a sink.
And the problem is??? Lol
NEC 240.81 – “Down” position of the breaker handle can’t be “On”.
Left/right ok, up ok, but not down for the “On” position, which is inevitable when mounting pretty much any US panel sideways.
This MAY be ok in Canada though.
Roy? 
I asked this question a while back and got this answer from the authority:
I inspected a house today where the panelboard was mounted sideways ie. horizontally. The top row of breakers were “on” in the down position.
It’s my understanding that this is not allowed in the US. Is it OK here?
Answer
Panel boards are permitted to be mounted in any orientation provided that the manufacturer’s installation instruction do not say differently. Different orientations include main breaker at the top, to the side, and at the bottom. (Rule 2-034)
Reference is to the Ontario Electrical Safety Code 23rd Edition/2002.