I was making those little shelves so I could fit all my Discworld books on one shelf and realized I have had a specialized skill for like 20 years that might be helpful to other crafty types. So:
How to Cut Cardboard/paperboard/etc Shapes with Straight Edges like a Design School Flunkout
You will need:
-Cork-backed metal ruler
-X-Acto knife or similar craft knife
-Self healing cut mat
You can probably find all of these things at your local art supply store; if there isn't a good art supply store in your area I favor Blick for buying most of my art supplies online. If you're on a tight budget or trying not to buy anything new I'd also recommend regularly checking the office supply section of your local thrift store, especially for the rulers, or looking up creative reuse centers in your area. They're essentially craft supply secondhand stores and they're wonderful.
If you think doing this kind of craft is going to be a very rare occurrence, check to see if your local library has a maker space or craft room, they likely have all these things available to use there.
-The cork backing on the ruler is going to help the ruler grip to the surface and give it a little bit of space from the surface. This will make it easier to rest your blade along the edge and get a straight cut. It is important that it's made of metal so you're not accidentally cutting into the ruler itself. These things *will* last forever and are fairly cheap.
-I strongly recommend you put a fresh blade on your craft knife every time you use it. Cardboard and paper dull a blade so dang fast. (that's why your mom was so upset when you used the Fabric Scissors on Not Fabric) Also a sharper knife requires less pressure and less pressure means more precise control and more precise control means you're less likely to accidentally hurt yourself. One more safety note: I wrap the cutting edge of used blades in masking tape before I throw them away. Like so:
-I'd say the cut mat is the least essential item on this list. I personally have two: a very large one that lives on my craft table and a smaller one I've had since design school that is part of my "travel" printmaking supplies. They were a smart purchase for me because I do block printing and use the larger mat to cut fabrics with a rotary blade (I'd love to tell y'all I sew all the time but mostly I'm cutting the necks out of T-shirts for Sensory Reasons) and the occasional paper craft. If it's not worth the money for you I'd recommend using a couple of layers of cardboard or a foam mat and maybe doing your cutting on a surface you can damage without consequence. We're going to be using light pressure to make these cuts, but at the end of the day the goal is to cut *through* the cardboard so there's no way you won't cut into your working surface.
Not strictly relevant and definitely not mandatory but I got this little usb-rechargable "desk vacuum" from World Market to keep my coffee station clear of grounds and it's proven handy for little scrappy crumbs on craft projects. I've had it for a couple of years now, I think, and a few months ago I thought it was starting to wear out but I just had to remove and clean the bottom section; the little air screens had clogged up with fine coffee grounds and now it works perfectly again. Also it is very cute. LOOK AT IT.
Okay that's enough tool talk let's get into it!
Step 1:
Make sure that the entirety of the line you want to cut is on top of your cut mat. I know this sounds silly but it is a mistake I have made and my poor craft table has suffered. Then you're going to place your ruler against your guide line and put just enough pressure on it that it won't slide around when you're cutting. Use whatever grip feels most comfortable as long as you have 2 or more points of contact to keep the ruler in place. IT IS VERY IMPORTANT that your fingertips/knuckles do not extend beyond the edge of the ruler! Again, it sounds silly to say this but take a second to double check this for your fingies' sake.
Step 2:
Rest your craft blade against the edge of the ruler and cut along your line using very light pressure. Repeat this cut over and over until you cut through the cardboard. Using these light, repeating cuts allows you more control and precision which makes for better results *and* means if your blade goes off course you're likely to catch it before you cause an injury. I also tend to rest the pinky of my blade hand on the table for more precision. Again, note the fingertips as far from the edge of the ruler as possible, and always be aware of where your non-cutting hand is in relation to your cutting hand.
The main takeaway here is that light, repeated cuts will give you much better results than a single heavy cut, along with being safer and easier on your hands.
Bonus tips:
-If you're cutting an outside edge you can cut a little extra on either side or cut the cardboard all the way across to make sure the cut goes through the material completely. For inner edges/corners start at the corner and cut outward when possible to make sure you don't overshoot it.
-If you need to make a fold in your cardboard, score the line with a single light stroke of your blade. For corrugated cardboard I've had the best luck with scoring the inside of the fold; for paperboard (think cereal or soda boxes) posterboard or anything thinner, scoring the outside of the fold is most effective.
