There are a number of ways to fit an oil painting on canvas stretcher bars into a frame. One of the main issues that frequently occurs is that the frame is often shallower than the canvas stretcher so the canvas will protrude from the back of the frame. I have seen many ways to overcome this problem including nailing straight through the canvas stretcher bars at an angle into the frame or bending nails over the back of the stretcher. Z clips are also a favourite which are both hammered into the side of the frame and the top of the canvas stretcher. All of these techniques run the risk of damaging the frame and more importantly the oil painting whilst nailing and leave permanent holes in the stretcher bars if the oil is removed from the frame (for restoration or varnishing for example). A relatively new technique has become available which uses a simple screw-in bracket and these are called canvas offsets.

They are available in many different sizes but the great advantage is that they screw into the frame and can be easily reversed to take the oil painting out of the frame if needed. The canvas is completely secure and also there are no permanent nail holes through the canvas stretcher bars. Note the previous nail hole on this image to the right of the canvas offset shown.

They are very easy to attach to the frame and only a couple on each side are needed. Also this technique is classed as a conservation technique as the oil painting can easily be returned to it's original state before it was framed. There is another brilliant advantage of this system for artists who have just painted their oils. The oil can be fitted into the frame (once touch dry) and then can be easily removed when the oil paints are dry enough for varnishing. This should be at least 6 months to a year after the last paint has been applied and then the oil can be easily removed, varnished and replaced with the minimum of hassle.

A really useful technique with the minimum of risk to the picture.