Gaffers Tape is a much better choice over duct tape but it is quite
expensive and it too will leave a residue if hit by the sun.  Heed
Malcolm's comment about masking tape . . . it is the worst choice.
For a quick screen, use the magnetic strip suggestion . . . it works
well and -zip- and it's off.  If you have a sign shop in the area, check
with them - they often have extra strips around cut off custom magnetic
signs.  At least I do.    Marlin ...'87 Syncro