How would you build a 500mw laser level

Thanks for looking guys, I am hoping you will be able to offer some recommendations. I need steering. I want to build a laser leveler that:

1. shoots a single (horizontal) line at min 500mw (532nm) visible on a wall outdoors, visible in indirect sun at least.
2. that can be powered continuously for hours. Assume needing a corded laser
3. A mount with which I can tilt the beam up or down as I work up the wall (with siding/tile/stone) but will remain level horizontally.

I would be very grateful for how I could make this work! Thanks for sharing your wisdom.