You'll need four hands.
I consider myself a handy guy. I've assembled IKEA bunk beds, hung blinds, built stairs, cabinets. The Sidekick looked like a piece of cake. However, the instructions are in need of another go-round. Make the pictures bigger, Thule!! Also, to assemble the top piece to the bottom piece you really do need another person to help line up the hinges with the attaching hardware. That or turn yourself into The Rubber Band Man. Once the Sidekick is put together things get a tad easier.
Decent product and fairly easy install. Too expensive for my taste but needed the space. If you accidently let it open from both sides it is very difficult to get shut again, although it is nice to have the option of which side to open from. Just make sure you only open one side at a time. Also, didn't like the relitivly small opening for a fairly big space. My double stroller will not fit.