Simple Abrasive Organize

Hi everyone first of all i'm not good in English but I'll try my best

problem
when i bought an abrasive and store it in my garage  .By the humidity moisture or whatever  -- it always turn from a flat sheet to the circle roll it make me frustrated.  So I try to find out how to organize and kept it flat. 

Thing to make
- file 
- plywood ( as a back plate)
- wood / drywall screw 
- zinc plate

Tools
- utilities plier
- drill machine
- screwdriver


I look up for a scrap and  I finally use a file fastener ( I'm not sure what does it call  but it use to attach in the center of the file )
then I hack it and screw in to a back plate that i use 2*1 plywood.  After that i made a cover with Thin a zinc plate  FINISH !!

i also made an index by the grit number

It Simple but  hope you like it :)