Many users post their tools, models and scripts to the ArcGIS Resource Center, where you can download them for free and install them to use them. You can also share your own tools and toolboxes with each other. This video tutorial uses an example from Lab 6, Task 3 where you had to manually draw a polygon around the survey points to include in the creation of a TIN. Thanks to somebody by the name of Bruce Harold, a concave hull estimator tool exists and does this task for you with the click of a button. We use this as an example to show how you find tools, download them, and use them in ArcToolbox: