A shed is a popular and effective place to store items that you do not want in your house that need to be protected from theft and the weather. A shed built on a slope may start to lean over time, making the structure potentially hazardous. In order to make the shed safe and usable again you will need to level it. Properly leveling a shed takes a bit of time and know how.
Dig a hole beside one of the pier posts on the downhill side of the shed with your shovel. Make the hole flat and deep enough for you to place the bottle jack under the floor joist of the shed a foot away from the post.
Place the jack into the hole, close the pressure valve on the jack, and pump the jack to raise it to the bottom of the floor joist of the shed. Place your 4-foot level on the shed floor and have an assistant watch it to tell you when the floor is level.
Cut through the pier post with your reciprocating saw and lift the frame by raising the jack. Slide a 2 inch x 6 inch x 10 inch treated board between the top of the post and the bottom of the joist above. Add boards as necessary to level that side.
Dig a hole, place the jack, cut the post, lift the frame, and place boards to level the opposite side of the shed. Repeat on both sides as necessary to level the shed floor.
Remove the jack and allow the full weight of the shed to hold the boards into place. Drive a galvanized 16d nail up, at a 45 degree angle through each size of both posts, through the boards, and into the joist above.