[Short Hand]

Easiest way is to just define a pattern


1make a new photoshop file make it 1x2 or 2x1 "PIXELS"!!! doesnt matter just depnds if you want the lines to go horizontal or vertical.

2next zoom in as much as you can

3 colour in one of the pixels the color you want the scan line to be most likely black.

4 click edit > Define pattern > save as scan line 1 or whatever.

5 now to use this pattern click the layer on the image you want to have the scanlines then click edit > fill > choose your scanline pattern that you saved.

^ easiest way to make scan lines. Just dont whore them onto sigs it tends to piss of a lot of people round here.