IKEA Besta Manual page 29

Step 9
A. Obtain one of the support rails.
B. Insert anchor nut (#100514) into one end with a flathead screwdriver.
C. Insert the mounting tabs of the support rail into the corresponding holes on the chair leg.
D. Insert long shank screw (#122606) into the hole in the leg. Push it down until you feel contact
with the threaded insert in the support rail.
E. Turn the anchor nut to align the threads with the long shank screw. Once aligned, start threads
by hand. Use the Allen wrench (#100001) to tighten the screw.
F. Repeat this procedure for the other support rail.
Note: Be sure to use the long shank screw as shown in picture (i) above.