Building sets including a plurality of blocks and a plurality of clips configured to engage a thickness of one or more of the blocks. Each clip includes a base and first and second substantially parallel extensions extending from the base and defining a channel therebetween into which a thickness of a block is receivable. The width of the channel is substantially equal to and slightly less than the thickness of the block receivable within the channel so that the thickness is frictionally retained therein. The clip may include a magnet enclosed within the base so that the base of a first clip may be magnetically coupled to the base of another clip, and each clip may in turn be frictionally coupled to a block received between the extensions of the respective clip. In one embodiment, the clip includes a plurality of channels.