How to Install a Forend on a Remington 870 (Replace, Change)
UPDATE: Watch How to change a forend on a Remington 870 Video
Little instruction on how to install a new forend on a Remington 870 shotgun.
Warning: Be sure to check that your shotgun is unloaded.
What you will need to install a new forend on your shotgun: old forend, new forend, pliers:
What you need to install forend on a Remington 870
1. Disassemble your Remington 870 shotgun and take out the old forend.
2. There is a nut on the front of the forend. You need to unscrew it using pliers (insert them in two notches on the nut).
Nut with two notches, Remington 870 forend
Unscrew Nut on Remington 870 Forend
You can use pliers on your Leatherman multi tool if you have one. Some recommend to use a spanner wrench for this purpose.
3. When you have the nut unscrewed just slide the forend off.
Slide Forend Forward
Remington 870 Forend and Action Bar Assembly
4. Slide on new forend and reverse the process.
Slide On New Forend
That’s all, you have installed a forend on Remington 870 
Used these instructions to fit a new police forend on my express and even I couldn’t mess it up.Thanks.