First why?   Setup a closed area location to use wifi to communicate. I use a wifi 3d printer that doesnt have a display. I log in using a internet browser so I can manage many printers from my desktop. To have my printers in a controlled space I need to setup a access point, hard wired then 2.4 wifi. 

This is what your looking for:   

The Ethernet port of RE220 can easily turn your wired Internet connection into a wireless access point.

I purchased a TP-Link 220 used on amazon for 20 bucks. Note this is definitely a CHINA SPY device, the terms of use grants the CCP access to what your putting through the device so you have been warned, If the China Masters want to see what I am 3d printing thats ok for now, I will replace the device with a more secure one, this was just to make sure it would work.

Modify:
Remote trailer with 6 duet wifi controlled printers, trailer closes up with no wifi penetration  

   drilled a hole and ran a cat wire from the primary router to the 220 wifi device. 

First thing you have to change the mode of the device from range extender to access point. plug in the network and power.   

look at available network connections and select the tplink device network then run their address to connect , the ip is   http://tplinkrepeater.net or  http://192.168.0.254   once you connect it pretty easy sailing. when you restart the device it will show your new wifi network, name it something different so you can find it. I named mine 3dprint,this made it easier to config the duet wifi boards cause you have to tell them the ssid name so don't get to crazy. 

Once your setup you can log into the device from your regular internet setup, it will be like 192.168.1.12 when logged it the device will show who is on the 3dprint network, listing the ip addresses of the connected 3d printers. Just put their ip addresses into you current browser and the printer control panel of each machine will open.

If your wondering why I have this setup it's because I am sitting at my desktop terminal in my shop and am able to manage printers in another location