Introduction: this will show you how to create a cool looking screw to throw in your next tech or grunge graphics.
We'll start out with a nice looking grungey, metal, or rusty looking piece to cut from. I used this.

Go ahead and use this for your screw.
First start with your ellipltical marquee tool located here.

while holding shift click on the image making a circle to your desired size.

Right click inside the circle and select "Layer via Copy" then press ctrl+J to duplicate the layer.

Now that we no longer need that top layer let's get rid of it. Delete the top layer

You should now have something similar to this.
Check HereNow on the very top circle layer, go to your blending options and check off drop shadow, bevel and emboss, and stroke. Set you options to these settings.
Drop ShadowBevel + Emboss1 px strokeYour top layer should now look like this.
Check HereNow take your rectangular marquee tool located here.

Then make a rectangle with the top layer selected, ceter it as much as possible.

Press delete and get something like this.
Check HereNow go to Select>Transform selection to do this, again center as much as possible. Press delete again.

Now add a 1 px stroke to the bottom circular layer.

Your screw should now look like these.