Whether you are building a fence or a playset for the kids, setting the posts is an important part of the job. The posts support the rest of the structure, so they have to be securely anchored, sturdy and perfectly plumb. Since they go in first, they can also hold up progress.
Using fast-setting concrete allows you to simplify and speed up the process because it can be mixed with water in the hole. And, it sets up in just 20 to 40 minutes, so you can quickly level things up and move on with the project.