Figure 1: An open spin chain engineered on the surface. Spins (arrows) are accommodated at iron sites (spheres). A thermal average of the vector spin chirality ${\kappa }_{i,i+1}$ formed by two neighboring spins ${\mathbf{\text{S}}}_i$ and ${\mathbf{\text{S}}}_{i+1}$ at site $i$ and $i+1$ always points to the $y$ direction because of the antisymmetric Dzyaloshinskii-Moriya interaction implemented by the artificial structure. The magnetic field $h_z$ acting on an edge pins the otherwise fluctuating spin spiral over a whole finite-size spin chain.