If you buy furniture at IKEA Vernier, you might be tempted to use their assembly service, to save yourself time and sweat. Don't do it.
I have used this service several times when I moved, and only later realized the mistake. IKEA uses underskilled and (probably) underpaid workers which generally do a half-assed job.
My cupboards had handles which were not aligned. The bed had panels mounted the opposite way. The sofa wasn't even stable because one of its foots was mounted in the wrong place. To save time, I realized the IKEA workers didn't even use all the screws and pegs.
But the crappiest job they did was with the bookshelf: the top was mounted in the wrong direction, and since the wooden pegs couldn't obviously match, the workers fixed the top by badly drilling 3 screws on it. This was such a crappy job that I actually took pictures and sent them to IKEA to complain, but never received an answer.
If you aren't really keen in mounting IKEA furniture, you can find someone on the Glocals "Classified" which will do a good job for half the price.