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We investigate a characterization of hard-to-detect bridging faults. For circuits with large numbers of lines (or nodes), this characterization can be used to select target faults for test generation efficiently, when it is impractical to target all the bridging faults (or all the realistic bridging faults). We demonstrate that the faults selected based on the proposed characterization are indeed hard-to-detect by performing the following experiments. 1) We show that the fault coverage of a given test set, with respect to the selected subset of bridging faults, is lower and more sensitive to the test set than the fault coverage obtained with respect to a random subset of bridging faults of the same size, with respect to the complete set of bridging faults, and when possible, with respect to a subset of realistic bridging faults of the same size. 2) We demonstrate that a test set generated for the selected subset of bridging faults detects other bridging faults more effectively than when a test set is derived for a randomly selected subset of bridging faults of the same size. We also describe an efficient procedure for selecting hard-to-detect bridging faults according to the proposed characterization. This procedure avoids enumeration of all the faults in order to select the hard-to-detect ones. This is important for large circuits where even enumeration of all the bridging faults may not be feasible.