We use the weighted backpack as a means of "heavy work" for Ellie's motor sensory seeking.
You want to start off slow and then work your way up to 10% of your child's weight. You can use something simple such as rice or dried beans. Some people uses poly pellets but those are more expensive and more difficult to find. I used rice.
You will need:
2. Ziplock bag
You want to find a backpack small enough for your child and preferably with those waist straps to prevent back strain. I had a difficult time finding one small enough for Ellie and I ended up in the baby section at Target. I bought what I swore I would never buy--a child leash/harness. Oh yes, I did. However, I am not using as a leash. The leash is detachable and I did just that. I removed it. What is left is an adorable bear backpack small enough for Ellie and it clips in the front. Ellie weighs about 20 pounds and I have the pack straps adjusted as tight as possible.
Measure rice/beans. Our therapist recommended starting out at 1/4-1/2 pound. I used a food scale and made sure to "zero" out the ziplock bag.
Fill bag with rice, seal tightly and secure safely into backpack. I had to be sneaky and clever. Ellie cannot know this is really a backpack or she will open it and remove rice.
For our therapy purposes, Ellie only wears the backpack for 10 minute intervals. She wears it before she needs to be settled down for an activity such as speech therapy, organized play (ie flashcards, shape sorter, etc), restaurant. again, the mentioned weights and length of times are based on Ellie's specific needs and have been recommended by her therapist.
Most recently, I had Ellie wear the backpack as we walked from the car to Speech Therapy office and then while we were in the waiting room. Did it help? I don't think so, but again, we only have ~1/4 lb of rice in it.