The ball bearings and tracking were really a challenge as other reviewers mentioned.  After getting lunch to come down from the excitement I decided to take out the tracking and just insert the shelf without it, which works perfectly for me.  I use it in my office as a catchall for items I might use during check out, lablels, receipts, payment devices and info, business cards and paper info plus info for refferals on top, and it does this quite beautifully.  I love it actually after deciding to circumvent that one part of assembly.