Most of the time, when we stamp images, the placement may not need to be exact but there are times when they do. Like when you are layering stamps or trying to avoid stamping on a particular part of a card, or if you are stamping a background, getting it central to the paper.
There are special craft items you can buy for this, but not everyone has a limitless budget or the space to store them. This method uses stuff you probably have lying around and is good enough for what we need.
You will need a ruler, craft knife, a stamp block, a placemat, temporary glue spray, and some permanent glue and some craft foam. If, like me, you have a Silver Bullet, you can use that to cut the foam. (I didn't, because my laptop was downstairs and I was too lazy to go get it!)
Here is the video
There, wasn't that easy? I glued the two layers together, matching up edges, to make it more sturdy. Make a paper tape measure for it as well if you think you may need it and glue that on top. Keep it with your stamps, so you don't forget you have it!
Here is a file for a print and cut ruler. It may not be 100% accurate, but it is near enough for this purpose. It is in SCAL format. Check the width is right for the cut outs you make and adjust accordingly.