AppleScript: Move files via drag and drop

I need to create workflow that allows the user to drop files onto the application and then have those files moved to a particular folder to be processed based on their file type.

So far, I've not got past the drag, drop, and move part!

on open theDroppedItems
    repeat with a from 1 to length of theDroppedItems
        set theCurrentDroppedItem to item a of theDroppedItems
        tell application "Finder"
            set folderSpool to folder "Spool" of desktop
            move a to folderSpool
        end tell
    end repeat
end open

When I do the drag and drop, I get:

Handler can’t handle objects of this class. Finder got an error:
Handler can’t handle objects of this class. (-10010)

I tried item instead of a, but that gave me the same error.

It's been a long time since I used AppleScript…