first how it is work
In order do make your own Ethernet splitters you'll need the following
Two RJ45 Crimpable Plug
Four RJ-45 keystone jack
Short Ethernet Cable Scrap (approximately 2 feet)
The tools you'll need:
RJ45 Crimp Tool
110 Punch Down Tool
Loctite Super Glue
Crimp the RJ45 Plug to the ethernet cable
...using the following wiring scheme
Taken from the excellent Hardware Book: www.hardwarebook.net/cable/network/ethernet10basetstraightthru.html
now 3Punch down the other end to the RJ-45 keystone jacks
Take the other end of the cable, cut it to 9 inches and punch down the four pairs using the following wiring scheme:
1 White/Orange to pin 1keystone jack
2 Orange to pin 2 keystone jack
3 White/Green to pin 3 keystone jack
6 Green to pin 6 keystone jack
4 Blue to pin 2 keystone jack
5 White/Blue to pin 1 keystone jack
7 White/Brown to pin 3 keystone jack
8 Brown to pin 6 keystone jack
Once all the pairs are punched down, you can glue together side by side the two keystone jacks.
Make one more splitter
using the previous information so you end up having two splitters.
Plug one splitter to the RJ45 wallplate
... and plug the two computers to the splitter.
Plug the other splitter to the patch panel
...and plug two patch cords from the splitter to two free ethernet jacks from the switch. If your splitter connections are right the two leds "LINK" from the switch on which the patch cord are connected should turn on.
We now have two computers simultaneously connected using only one ethernet cable. This method is similar to PoE (Power over Ethernet) but instead of injecting DC, it is injecting another "data".
But again, it is better if you can to pull one more ethernet cable from the patch panel to the wallplate. But in some specific cases, the Ethernet "splitter" can help out.