If you do not want to manage individual Forge mods, many popular, legal PvP clients feature built-in, togglable fast-place or custom crosshair/bridging utilities optimized for 1.8.9:
Opponents watched in awe from their islands. "He's using a Pro Placer !" someone shouted in the chat. Jax didn't stop. He felt like a master of cobblestone, his movements fluid as he reached the center diamond generator before the first team had even finished their wool defense. The mod worked perfectly, stripping away the artificial delay and letting his true speed shine. By the time the final bed was destroyed, Jax wasn't just a player; he was a legend of the 1.8.9 circuit, the boy who built faster than the eye could see.
onTick(): if placeKeyHeld and timeSinceLastPlace >= placeInterval: target = findPlaceTarget() rot = computeRotationTo(target) applyRotation(rot) # client-side yaw/pitch sendPacket(PlayerLook, rot) sendPacket(UseItemOnBlock, target) recordAttempt(target, now) timeSinceLastPlace = 0
Several versions of this mod exist with different specific mechanics: FastPlace (Standard)