The list author says: "You can build your own pulley logic gates!
See a demo here: bit.ly/pulleylogicgates See pictures here: bit.ly/pulleylogicgatespics
In addition to this stuff, you'll also want: 1) Three keychain rings, for the input and output 2) Some pieces of wood, such as 2x4s, for the base 3) Something big and heavy, such as a large book, to keep the chessboard standing, if the base you use isn't heavy enough 4) A hammer, for inserting the nails as well as getting small holes started to insert the eye bolts in to 5) Four nails, for setting the inputs as well as making the small holes mentioned above 6) A pair of scissors, for cutting the string and twist ties
Although these are the materials I used, there's not necessarily anything special about them, and you have a lot of flexibility. For example, you could use a piece of plywood instead of the chessboard, or some heavy bolts instead of the physics set weights."
"These do all the heavy lifting! You can use any set of weighted objects, for example some heavy bolts. You'll need minimum one light weight, two medium weights, and one heavy weight to build all of the logic gates. They do need to be significantly different in order for the gates to function, though they don't need to be any exact weights in particular."
"These are for hanging the strings. It's important to use eye bolts instead of hooks, so that the strings don't slide off when they're not taught. However, it's also convenient to use eye bolts with small slits so that the strings can be slipped in and out when assembling and disassembling."