Crosshair

The story is that I want to test LUA in singleplayer and I have alaready tested many stuff.
But I was wondering how do I make a crosshair? Since I have been searching all around Facepunch,Gmod lua wiki, google. I did found some crosshair but they dont appear.
Can I have a code for a crosshair? or a code for a Laser Crosshair what points out from the gunbarrel.

~Holo

I’m interested in the laser one as well was just about to post a request for that.