how to draw such a line?

[iMac1943]

How can I draw a square like this in AD?

[v_kyr]

That looks more like a reused frame image, like these here (grunge frames). - Though with some irregular brushes and applied brush strokes you can get similar looking worn out line effects.

[iMac1943]

Thank you. I'll give it a try.

[firstdefence]

You can make your own intensity brush using the pencil tool.

Create the Brush texture

1. Draw a black rectangle (No Stroke)
2. Select the pencil tool (N)
3. Change the stroke colour to white and the fill to none
4. Start drawing lines until you end up with something like this
   
5. You could also vary the tone of the stroke to 50 shades of grey to give some kinky tonal contrast lol!
6. Select all of the strokes - you can group them if you want.
7. Export as a png file (selection with background) remember where you saved it.

Create the intensity brush

1. Open the brush panel
2. From the burger menu select New textured intensity brush
3. Use the png file you exported previously as the texture, you should now have a brush that looks like this
   
4. Create a square, fill as white or none and stroke as brush, you should now have something like this
   

Now go mad creating all manner of brushes

[iMac1943]

That is very interesting! Thank you. What a fantastic community!

[iMac1943]

4 hours ago, firstdefence said:

New textured intensity brush

YEAH!!!!! Thank you firstdefence!!!