This is one type of fast tracking portal weighting instrument. It appears several thousand years ago and is still valid today. The weight scope can vary according to your sling weight if you have exact amount of water. There are many factor affecting the precision, this design tries to improve it in simple steps.

Step 1: Material Preparing

Lever scale is one ancient instrument for weight measuring. It is simple and easy to use. Of course, with not-so-good accuracy. But enough for you to weight your fruit in grocery. This level scale is almost made of paper excluding two paper clips, it can achieve 5% deviation with little adjustment.

To make this you will need:

1 x poster paper
1 x white paper A4 size
1 x 1ft lengths cotton line
2 x paper clip
1 x bottle mineral water 390ml
1 x plastic bag

Tools,

1 x Glue
1 x needle
1 x pen
1 x ruler
1 x scissor
1 x tape, optional for extra strength

Step 2: Rolling the Paper Level

1. Roll up the poster paper, starting from one corner in 45 degree diagonal direction. This is much easy to roll up the paper tight and hollow paper roll in one end is good for deviation alleviation. Glue the paper both at start corner and terminal corner, to make the roll solid and tight.

Then, cut part of the paper roll from the start end to adjust the length and leave the solid part of the roll. This part shall be strong enough to hold total weight.

2. Cut one slice of white paper and roll it around the roll already made for next step of marking lines. Glue is needed in this stage too.

Step 3: Weight Sling

1. Pass the cotton line through the leading hole of needle. Press the needle into the center of solid part, make the line even in length in both end, then tighten one knot to make it a ring sling.

2. Press the needle again with a new cotton line into the paper roll again in 90 degree direction , to make it a level. Fix the line to.

3. A prototype paper level scale is ready now.

Step 4: Marking

1. Marking is one important step in level scale. First, the original point shall be marked with 0, where the holding sling affixed.

2. Then the short end shall be marked -1, and the rest of lone end shall be marked evenly with same measuring step. In this case, +6 is for longer end. This means the maximum scope shall be 6 times of the sling weight.

3. It is good practice if you can mark the line in clean paper first, then mark the line in the paper level scale accordingly.

Step 5: Weighting and Completion

1. Attached paper clip in sling line in both end.

2. Pour the 355ml water into one empty plastic bag, and attached it to sling in the the longer end. Use this as 355g sling weight.

3. Attached the fruit and vegetable in another bag to paper clip in shorter end.

4. Move the weight sling alone the level scale until the level is horizontal and balance stage. Read the mark value in the level scale. In this case, the weight of one green pepper and one red pepper is,

355 x 1.8 = 639 g

Now, the portal fast tracking paper level scale is made and test.