There are myriad [2]catenanes and [2]rotaxanes that consist of two interlocked molecular components. On occasion, supramolecular chemists prepare interlocked molecules where there are covalent linkages between the interlocked molecular components. In this review, progress on pretzelanes ([1]catenanes), [1]rotaxanes and molecular figures-of-eight is surveyed. Particular attention is paid to the application of such molecules, especially where the interlocked structure and/or the covalent linkage(s) play a key functional role.