The Mark Bind tool is a more precise version of the Bind tool. It allows you to select a collection of paths one at a time to be added to a single bound path. After you’ve initiated the binding by touching anywhere on the screen, drag your finger to a Snapping Point of a path and press the Mark Button. The path will be added to the bound collection. Continue this process until you’ve collected all the paths that you wish to bind together. You have a few options for how the final binding will be created. You can create a normal Bind which will add all the paths to a single bound path, or you can create a Copy-Bind which will create a copy of each path and then bind the copies together. You also can decide how the bound paths will be rendered. A normal binding renders the paths as if they were simply glue together as separate objects at their original Z levels. A Layer Bind renders every path one paint layer at a time, first drawing the lowest paint layer of each path in the collection, then the middle layer, and finally the top layer. This can produce some interesting and otherwise difficult to create effects. Lift you finger to finalize the binding. For more information on binding and layer binding see the Bind tool.
Here’s an example of marking bind: