A Puzzle about Fuses

You have 2 lengths of fuse that are guaranteed to burn for precisely 1 hour each. Other than that fact, you know nothing; they may burn at different (indeed, at variable) rates, they may be of different lengths, thicknesses, materials, etc.

How can you use these two fuses to time a 45 minute interval?

Note that because the fuses may burn at variable rates, and because you have only two fuses to work with, strategies involving cutting the fuses and/or determining their properties by experiment are doomed to failure.

Don't look at this hint until you're truly frustrated.