I have a leaking brake caliper that I won't be able to repair until after the new year. (Related thread here: Leaking brake caliper - 82 300D.)

So that I don't lose all of the brake fluid in the reservoir, what's the best way to temporarily clamp off the flexible brake line to this caliper without doing any permanent damage to the rubber?

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05 E320 CDI - 185K miles
82 300D - 200K miles (sold)