The Simple 2x4 Pyramid
This page provides general links to different tools and materials that you might need in order to build your pyramid. I receive a small commission from anything you buy on Amazon, which helps to keep my business going.
If you are planning to connect your 2x4s together using duct tape, I recommend 3" Gorilla tape due to its strength. But you can also use a tan-colored tape if you want it to match with the wood better--just don't have the kids use it as a jungle gym (actually, don't have the kids use it as such unless you are using metal brackets).
If you are going that route, in addition to your local lumber store, there are several options on Amazon: a pack of 20 stainless steel brackets, a larger galvanized version, or a heavy-duty version.
If you are choosing to use plastic brackets, there are 24 of them, so I would use two per joint (like in the pictures). And regardless of whether they are plastic or metal, if you are using brackets, be sure to use 1-1/2" screws. There are also options for a 300 pack for not much more.
If you are doweling your pyramid together, then I highly recommend getting this drill guide. You will most likely also need a 25/64" bit, and there are also larger sizes available (like 13/32") if needed. Alternatively, you can get a set, like this 29-piece set, instead. I have found that the 3/8" chuck on my drill can handle 25/64" bits and just barely 13/32" ones. If you think you might need to use larger bits, consider this drill with a 1/2" chuck, and is corded, which will give you more power than most cordless varieties. You will also need 1" x 3/8" dowels. This 100-pack has good reviews and should be plenty for your pyramid. And if your dowels are loose and you need to glue them in, this is the best choice.
If you think you might need to disassemble your pyramid in the future, this pry bar could be very helpful, as well as a good mallet.
And finally, if you are planning to make your cuts using a hand saw, here is a good option if you don't have one already.
You can also find other tools that might be helpful in building whatever pyramids you might choose to make, including things like clamps, tape measures, squares, drill jigs, wood glue, drills, miter saws, circular saws, and much more on this page here.