A method used in forming a memory array comprising strings of memory cells comprises forming a stack comprising vertically-alternating first tiers and second tiers. Horizontally-elongated trenches are formed into the stack to form laterally-spaced memory-block regions. The memory-block regions comprise part of a memory-plane region. A pair of elevationally-extending walls are formed that are laterally-spaced relative one another and that are individually horizontally-longitudinally-elongated. The pair of walls are one of (a) or (b), where: (a): in the memory-plane region laterally-between immediately-laterally-adjacent of the memory-block regions; and (b): in a region that is edge-of-plane relative to the memory-plane region. Through the horizontally-elongated trenches and after forming the pair of walls, sacrificial material that is in the first tiers is isotropically etching away and replaced with conducting material of individual conducting lines. Other embodiments, including structure independent of method, are disclosed.