Here's an easy and effective way to manage screws, washers, and other small parts that you need to transport or want to store with the hardware that they belong to. I find it most useful when I'm removing usable parts from broken computer hardware.
Step 1: The problem
So here I am in the office. I've removed the parts I wanted from a broken PSU, but the screws and washers are going to be hard to transport home without a container. I could use a small sandwich bag or a box, but usually I don't have those handy. So I'll use packing tape.
Step 2: Prepare the tape strip
Grab your packing tape roll and pull off an appropriately-sized strip. For this example, I used roughly a 3" long strip.
Now fold the top and bottom edges over on themselves so that you have tabs. These will be used later to open your bag when you're ready to remove your screws. See the picture, below.
Step 3: Add screws
Add your small parts to the middle of the tape strip, leaving a border all around, as shown below.
Step 4: Wrap it up
Now fold the tape in on itself so that the top and bottom tabs meet. See the first image, below.
Press the sides together to seal the small parts inside. See the remaining images.
Step 5: Finished
You can now transport your little bag without losing the contents.
To open the bag, just pull the tabs apart.