This specification covers steel derricks@ steel substructures@ and standard rigs. It includes stipulations on materials@ design features@ loadings@ and allowable stresses. Recommended practices on the erection@ care@ and use of steel derricks are included as an appendix. Nothing contained in this specification is to be construed as granting any right@ by implication or otherwise@ for manufacture@ sale@ or use in connection with any method@ apparatus@ or product covered by letters patent@ nor as insuring anyone against liability for infringement of letters patent.