Abstract: An improved fastener indicates when a predetermined preload has been applied to the fastener. The fastener includes a body section which is connected with a thread convolution. A load transmitting and indicating section is connected with the body section. The load transmitting and indicating section includes a bearing section having a flat annular bottom surface and an undulating annular spring section which circumscribes the bearing section. The spring section has a bottom surface with crest and trough portions. The crest portions extend tangentially to the plane of the bottom surface of the bearing section. The trough portions are resiliently deflectable toward the body section to flatten the undulations in the spring section upon application of the predetermined preload to the fastener.