Squeeze the sides of the jack so you dislodge the holding tabs at the bottom of the cover from the slots at the edges of the jack panel. Pull the cover up off of the jack panel and put it aside. Older biscuit jacks have a screw at the center of the jack cover. Loosen it and then lift the cover off the jack.

Thread your phone or Ethernet cable through the half-moon shaped opening in the bottom rear of the jack. Pull it out through the hole in the center of the jack.

Strip off about 1 inch of the thick gray or white insulation that covers all of the wires of your phone or Ethernet cable. Strip off about 1/4 inch of insulation off or each of the four wires of your phone cord, or each of the eight wires of your Ethernet cable.

Loosen each of the four terminal screws of your telephone jack, or each of the eight screws of your Ethernet jack. The screws are located at the top of the back panel of the jack. Skip to Step 6 if you are hooking up an Ethernet jack.

Match the red telephone wire from your phone cable to the jack that is connected with red wire from under its terminal screw to the plug end of the jack. Wrap the red phone cable wire around that mounting screw and tighten the screw with your screwdriver. Repeat for the black, green and yellow wires and make sure each color of phone cable wire matches the same color jack wire.

Face your Ethernet jack up so that the plug end is on top. Note the color of each wire inside the jack that is connected from a terminal to the plug end of the jack. Connect standard Cat-5 Ethernet cable as follows: White-orange Ethernet cable wire to green jack wire terminal; orange cable wire to yellow terminal; white-green cable wire to brown terminal; blue cable wire to gray terminal; brown cable wire to blue terminal; white-brown cable wire to orange terminal; green cable wire to black terminal and white-blue cable wire to red terminal.

Test the jack by plugging in a telephone or Ethernet device and making sure that it works. Listen for a dial tone when testing a phone and then dial your own mobile phone and make sure your mobile rings. Test an Ethernet jack by plugging in a cable and running it to your computer. Turn the computer on and check your system tray for an indication that you have plugged in an Ethernet device.

Remove your phone or power off your computer. If there are any problems, double-check to make sure each cable is connected properly. If the cables are connected properly, your jack is defective and you should replace it and repeat Steps 1 through 7 with a new jack.

Snap or screw the front cover back onto the biscuit jack panel once you are certain that the jack works properly.

Peel off the backing of the mounting tape on the back cover of your jack and press the jack onto a wall or other flat surface such as the back of your desk if you want to mount your jack. You can also leave it on the floor if you wish so long as it is in a place where it will not be stepped on or otherwise crushed.