1. User defined element 1.1. Data group identifier, one input line USERdefined ELEMents 1.2. Specification of elastic contact surface(s), NUSREL lines NUSREL NUSREL : integer: Number of subsequent input lines for specification of user defined elements. 1.3. User defined element type, three input lines per element type, i.e. NUSREL*3 input lines One line USRELNAME USRELNAME: character(): Character string giving path and filename to the dll One line USERINPFILE USERINPFILE: character() : Character string giving path and filename to the dll input file One line ELTYPE LINE-ID ISEG IEL USERID VERSION ELTYPE: character(8): Element type = EARTH : earth element type spring LINE-ID: character(8): Reference to a line identifier ISEG: integer/character: Local segment number within line LINE-ID = ALL: All segments in specified line IEL: integer/character: Local element number within segment ISEG = ALL: All elements in specified segment USERID: character() : User defined id. The ID can be used in the dll to differ among the element types VERSION: integer : Version number = 1: implemented Description of the input and the interface for the external userdefined element is given in External dll.