Saturn square Lilith (orb 1.6°) creates concrete friction between the two planets. The orb is very tight; this describes a stable character pattern more than a passing reaction.
Here, Saturn in Sagittarius in House 4 brings discipline, constraint, endurance, and mastery into House 4 (roots, privacy, and inner foundation), with Sagittarius style (expansion, travel, belief, and the search for meaning); Lilith in Pisces in House 8 brings pure ideal, absolute demand, fascination, and refusal of compromise into House 8 (sexuality, shared power, crisis, and invisible bonds), with Pisces style (imagination, faith, compassion, dream, and permeability).
Concrete friction: this aspect puts Saturn (discipline, constraint, endurance, and mastery) and Lilith (pure ideal, absolute demand, fascination, and refusal of compromise) into repeated friction: one can interrupt, inhibit, or provoke the other in concrete situations. House 4 (roots, privacy, and inner foundation) is in friction with House 8 (sexuality, shared power, crisis, and invisible bonds); this can create blockage, inhibition, overreaction, or repeated conflict between the two fields.