Error filter: an aggregate of oligomers (introduced in Section 2) with specific sequences. Hairpin Assembler (HA)-device: assembler allows gapless binding of hairpins. This kind of aggregate is selected in the evolutionary process because all monomers are complementary paired, thus the aggregate is protected from hydrolysis. It is assumed that the aggregate is further stabilized by adsorption at a flat surface. This fundamental evolutionary process requires an environment that must strongly change when proceeding from the selection-to the multiplication-phase. In multiplication-phase the aggregate has to dissociate forming single oligomers that replicate. Simplified representation: it is not indicated that hairpins are assumed to be helical and homo-chiral to precisely interlock. The assumed simplicity of a (HA)-device should focus on the essence driving to bio-life's origin. Chemical reality can be much more involved. Monomer binding sites are indicated by arrows. (+)-hairpins (templates) and (-)-hairpins (replica) have identical sequence of monomers, except the second monomers in the triplets that are complementary. The first and the third monomer in the triplets are complementary leading to a reading frame in the sequence of monomers in the assembler (green).