Some airlines (not UK based) have a system where the crew will enter defects in the tech log as is usual. The defect will be fixed and the log certified as usual, in addition to this the work also has to be recorded on seperate maintenance sheets, of which there is only the one copy and it is not left on the a/c of course, so in effect doubles the paperwork. However the entry in the t/log to clear the defect does not have to give full details, but refer to the maint sheets, however most engineers do enter in the log what has actually been done (as well as on the maint sheets). But....any other work, not relating to a crew entry, say brake found worn, this is only certified and recorded on the maint sheets..no record at all in the tech log....