It holds the thread spools in high density (capacity of 175 per box), but so that the colors are all visible.
It keeps matching spools and bobbins together on the same peg.
It's portable, compact, and neat. The box can be stored in any orientation without making a mess of the thread, and the clear plastic allows the contents to be instantly identified.
The box in these pictures is only half-filled (8 rows out of a possible 14).
Step 1: Gather your materials & tools
1 - ArtBin Super Satchel, single compartment, not slim, not with thread insert (available at Jo-Anns Fabric) - $14.49 ea
7 - ClosetMaid Tie & Belt Racks (available at Home Depot) - $5.47 ea
2 1/2 feet wood trim (I used 3/8 inch by 3/4 inch artificial wood quarter round from Home Depot)
3/16 inch drill bit
Adjustable wrench (or something else to straighten the pegs)