Abstract: A generalized, rationally-scaled design is disclosed for a line laying system for use in stringing communications cable across inaccessible spaces. The system includes a tethered projectile which is accurately aimed and launched to a defined target zone by means of a energy-store coupled with a pivoting release lever. The geometric details of placement of the pivot axis of the release lever are disclosed in detail. Specific configurations of the projectile guides and spring support ribs are also disclosed. Implications of design and materials upon accuracy and range are considered and optimal component finishes and tolerances are indicated.