HOW TO RE-ASSEMBLE THE BLADE UNIT ON A WAHL 9590

SOURCE: How to reassemble blades on Wahl rechargeable unit

I had the same problem and I eventually figured it out. The blade assembly has to be reassembled first then snapped back into place.

1. the bottom part has a little "nub" that the screws attach to
2. the second part is the thin piece of metal with a ridge
3. the white plastic thing, make sure the ridges are sandwiched together
4. the small blade, the blades must face each other
5. the large blade

use the 2 screws to hold the assembly together, once assembled it snaps into place on the clipper. See attached picture for how it should look once assembled.

It's STUPID that this is missing from the instruction guide that comes with the clippers.

SOURCE: How to attach beard regulator on Wahl Groomsman

The attachment should hook over the teeth of the blades and then snap onto the back end.