Installing the handguards on the AR-15 is the last step in the assembly process and it goes a lot easier with a special tool designed just for that purpose. This handguard tool made by Schuster makes it a simple job to pull back the delta ring while we install the handguards.
Simply hook the padded tab of the tool into the magazine well with both arms of the tool hugging the delta ring. Now squeeze the arms and pull down. This will slide the Delta ring back and out of the way. Place the bottom half of the handguard on the rifle, hooking it under the handguard cap behind the front sight base.
Now repeat with the top half.
Holding the two halves together, you can release the tension on the tool, letting the delta ring move forward, capturing the rear of the handguards.