So I got this strange thing here: http://www.apple.com/shop/product/MK122LL/A/power-adapter-extension-cable
It says that
The Power Adapter Extension Cable is an AC extension cord that provides extra length for your Apple power adapter. Use it with MagSafe and MagSafe 2 power adapters and 10W, 12W, and 29W USB power adapters.
So I guess I can use it to extend the length of the MagSafe power cable? But how? I see no holes that fit it!
Also, I got this:
Which looks like the extension but without the cable part. Is this related?