Placing a pet door into a metal door differs from installing one in a wooden door, however it is still manageable by following these steps.
Step 1 - Measure Up
Read the fitting instructions that came with your pet door to find out how big the hole in the door should be. At the same time you should check to see how high above floor level the bottom of the door should be.
Step 2 - Mark the Bottom Line
Mark the line that marks the level of the bottom of the door.
Step 3 - Mark the Uprights
Using a set square, mark lines vertical to the bottom line to mark the outside edges of the required hole and then mark the top of the pet door.
Step 4 - Cut Out the Hole
Drill a hole in each corner of the frame you have marked out. These holes should be just large enough to accept a metal cutting jigsaw blade. If the door is double skinned, make sure you cut through both skins. Also make sure that the jigsaw is always at a 90-degree angle to the door while you are cutting. You should not hit any other metalwork while cutting, however, the space between the skins may be filled with foam.
Step 5 - Clean the Edges
Although they will not be exposed, clean the burrs of the cut edges.
The next steps will depend on what type of door you are fitting.
Self-framing Pet Door
A self-framing pet door is in a frame made up of two sides that telescope into each other. Insert the outer (female) side into the hole you have cut into the door then insert the inner (male) side. The two sides will be fixed by screws that will close the two sides together to grip the door. Flanges on both sides will prevent the pet door from falling out of the hole.
Standard Pet Door into a Double Skinned Door
Create a frame. If the metal door is twin skinned, you will need to measure the distances between the two skins.
The frame will be made of four pieces of timber that will be measured to line the inside of the hole in the door. To handle the timber easily, insert a screw in one edge of each. Using the screw as a handle, insert each piece of timber into the door to frame the hole. Glue each piece securely into place and clamp it till the glue is dry.
Remove the screws. Following the instructions that came with the pet door, insert the main pet door frame into the hole and secure it to the wooden frame you have created. Fit the other half of the frame and secure it. Connect the actual door to the frame.
Standard Pet Door into a Single Skinned Door
The frame will be made of four pieces of timber that will be measured to line the inside of the hole in the door. Using a strong glue, fit the frame around the hole in the door on the inside of the door.
Following the instructions that came with the pet door, insert the main pet door frame into the hole and secure it to the wooden frame you have created. Fit the other half of the frame and secure it. Connect the actual door to the frame.
Once you have the pet door frame fitted you can try the pet door for size by getting your pet to go through it.