Out of vinyl sheets? or you don't have one around then duct tape is your best friend.
I was spray painting my clock with matte black it came out good but I wanted it to give it a better look so I chose a duct tape i had lying around.
Step 1: All You Need
An electrical duct tape
a tape which is called I don't know what.(if you know please comment)
Step 2: TAKE THAT FRAME OUT
Remove the frame for better access
(the frame looks ugly for my spray painting skills they ended in a disaster and I sanded the frame ending in a very awkward situation.)
Step 3: Wrap With a Don't Know What Tape
Tape the frame with don't know what tape and cut it out with a blade like in the pic and do the same with duct tape upon the same. and then wrap the borders with duct tape.
Step 4: Screw It.
I mean back to the clock and you're done