Wood is super lightweight and soft, so while they predrilled one side of each mating point, the wood is not predrilled on the other.  But I only found one place where I split the wood with the screws.  They numbered each piece inside a joint, so the number will not be visible after assembly.  I found you need to use a pencil and number each piece externally as you go, so that after subassemblies are connected you well still be able to determine which pieces are in which subassembly.  Took me about three hours to assemble, but it was pretty easy.  It holds most of my garden tools, except for a couple of rakes whose handles were too long to fit upright on the right side.  Shovels do fit fine.