If you need a cheap quick and easy solution for securing your fence posts, try concrete Post-Mix. Each bag weighs 20kg and is waterproof and tear-proof. You can use it for any kind of fence posts or gate posts. Just add water to the hole and sprinkle the concrete post mix on top. Then, compact the post mix with a stick to get rid of any air bubbles. It will set in 5-10 minutes, so make sure you adjust the posts before then. You may need one or two bags per post, depending on the hole size. Post-Mix will make your fence sturdy and strong.