The following example shows chords built on all the degrees of the C major scale. In any key it is possible to build chords on each degree of the scale. This means that for every major scale, there are seven possible chords which can be used for creating keyboard parts and harmonizing melodies. These seven chords are called scale tone chords. It is common practice to describe chords within a key with roman numerals as shown here.
The B diminished chord contains the notes B, D and F. Like major and minor chords, it can be played in three inversions which are shown in the following diagrams.