First of all, you need to find the horizontal and vertical center of your stamp and mark that spot on the front of the block and bring that mark to the edges. This is easy to do with the four stamps I am now selling because they have obvious mid points and the stamps are only slightly smaller than the blocks they are mounted on. With other stamps, you might have to get your ruler out.
The next step is super easy if you have one of these fancy gridded cutting mats. If not, just make a grid on paper. Actually all you need is one horizontal line intersecting with a vertical line. Line your block up with the vertical line as perfectly as you can while positioning one of the pencil lines on the front of the block with the horizontal line. Hopefully the photo above makes those instructions more clear!
Hold the block steady and shift your razor sharp gaze over to see the back of the block. Make a pencil mark right where that horizontal line is. Repeat these steps with the other three pencil marks that you made on the front (stamp side) of the block.
The back of your block will look like this
Using a ruler or any straight edge, connect the marks that are opposite each other. Horizontal and vertical.
Now the back of your block looks like this. It looks a bit off because the stamp is not perfectly square on the block. This is the case most often with red rubber stamps and this is why I happen to think these guidelines are essential if you are going to do any sort of precision printing.
You can use a triangle or any thing with a perfectly square corner to check to be sure your intersecting lines are perpendicular. For most people and projects, a general idea of where the up-and-down and side-to-side centers are is good enough.
It is important to make your marks permanent. You can scratch them in with an Xacto knife blade, use a wood burning or stencil cutting tool, or simply draw over the pencil lines with a Sharpie or other permanent marker.
I hope this is helpful! Now that I am not burning guidelines in the mounted stamps that I sell, I have lowered the price. Now the different options are as follows:
mounted stamps = $10.00
unmounted single stamp = $5.00
unmounted sheet with all four stamp images = $12.00