This datapack will allow you to get some use from your Fences, Walls, or Gates you no longer need. Just put one Fence or Gate anywhere into the crafting window, and get back some of your materials you used to produce the item. Walls need 2 of the same type in any shape.
Here's what you get:

• • 1x any wooden Fence --> 1x Wood Plank of corresponding type
  • 1x any wooden Fence Gate --> 1x Wood Plank of corresponding type
  • 1x Nether Brick Fence --> 2x Nether Brick
  • 4x any Wall --> 3x stone block of corresponding type (e.g. 4x Cobblestone Wall --> 3x Cobblestone)

Be aware that by doing this you lose some materials, so you can't use this to save inventory space!

You can choose if you want to use all Fences+Walls+Gates or only one/two of them, e.g. if you only want to use the Walls portion of the datapack.

Installation:

1. Download this datapack
2. Put the zip file into your datapacks folder in "%appdata%\.minecraft\saves\(name_of_your_world)\datapacks"
   
3. If you don't want to use any part of the datapack, just delete the folder you don't want in the zip file in "Reverse Craft - Slabs & Stairs\data\reversecraft\recipes\"
   
4. Done

Let me know if you find out something is wrong or needs a change. Thanks and enjoy.