Trainers or, more properly, School Bayonets, are locally made items. They were not made in government arsenals or by government contractors; nor were they made to government specs. Dimensionally, they vary all over the place. Some will mount to a service rifle and some will only mount to the school rifle for which they were made. It just depends. School bayonets were used in local high schools, which had military drill as a required part of the curriculum. The Army used regular service rifles and bayonets for soldier training. School bayonets are made of soft steel and castings. They were for "no-contact" drill exercises. If you tried to use it in bayonet fencing it would just bend or break.