After switching from a 100% to a TKL keyboard I realized I really missed the "enter" key on the keypad. So instead of buying a full keypad ($5!) I bought an old membrane keyboard, traced out the "enter" key leads and soldered them to an Amoeba PCB. I had extra keycaps from the TKL keyboard (no keypad!) which is what I'll be using for the single-key. This keyboard also has room for expansion - I may use it for ESC or "back".