This is a really pocket-sized scale. Is super easy and fast to do and cheap.
I find it really useful when I need to weight small amount of things, like copper or sulfur for disinfect my plants.

Step 1: WHAT YOU NEED

MATERIALS:
-2 popsicle stick;
-2 pegs (like the ones in the photo);
-1 small carabiner;
-1 small keys ring;
-a piece of thread;
-1 short nail;
-1 small iron ring (I used one from the valve of the inner tube);
-2 small plastic bag of the same size;
-some bolts of different weight (1,2,5 grams)

Step 2: PREPARE THE STICKS

-Cut one of the stick in half and sharpen one edge;
-draw a line in the exact middle of it (lengthwise);
-draw a line in the exact middle of the intact stick (crosswise);
-make 2 holes at the edges of the intact stick and one in the side of the half stick (like in the photo).

Step 3: GLUE THE STICKS

Glue the sticks perpendicular to each other like in the photo.

Step 4: PLACE THE CARABINER

Place the ring in the hole of the short stick and the carabiner hooked into the ring.

Step 5: PLACE THE PEGS

place the 2 pegs in the holes of the long stick

Step 6: PLACE THE NAIL

place the nail in the middle of the intersection of the 2 sticks

Step 7: PLACE THE WEIGHT

Tie the iron ring to the thread like in the photo and hang it up to the nail.

Step 8: PREPARE THE WEIGHT MEASURE

You should find some bolts of different weight: at list one of 1gram, two of 2 grams and one of 5 grams (so you can arrive to all the measurements until 10 grams).
Otherwise you can make small balls of clay of different weight.

Step 9: PLACE PLASTIC BAGS

On one side of your scale you should clamp a small bag with your weight measure, and on the other side the other bag with inside the thing you need to measure.

Step 10: HOW IT WORKS

How it work is pretty obvious!
Just put some weight on a side and add things in the other bag until the thread will be perfectly vertical along the line you drew on the short stick.
Another way you can do it (instead of the thread and the iron ring) will be to place a little level horizontal along the long stick.