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 the thickness of the block receivable within the channel so that the thickness is frictionally retained therein. In one embodiment, the clip includes a plurality of channels.