Abstract: A non-rotatable digging tooth has a forward working portion designed to excavate dirt, with a rearward cylindrical shank portion of a configuration to be removably received within the circular bore of a support block. The block includes a forward projection which forms a shoulder having a face positioned substantially parallel to the axial centerline of the bore. The juncture between the shank and digging part of the tooth is provided with a shoulder made complementary respective to the shoulder on the support block so that the two shoulders confront one another. The confronting shoulders abuttingly engage one another and provide a resisting force which prevents rotation of the tooth respective to the block. The block can be attached to various different trenching and digging apparatus.