After layout design, the baseboard is the most important feature of any model railway. It will provide a solid base on which the tracks, buildings, and scenery depend. Without a perfectly flat and rigid base, the track could eventually become uneven, which will cause poor running, possibly derailments, and de-coupling. Not what you really want.
Unfortunately most railway modellers do not give sufficient consideration to the design and construction of their baseboards, and many are not skilled carpenters. A well built solid baseboard is an essential starting point for any model railway or diorama, and all of the parts listed within these baseboard categories will help everyone build that solid base.