Choose a vertical or horizontal plane, then you can click and drag to quickly and neatly place blocks on that plane. Use this to easily extend walls, floors, bridges or roofs.

Clicking and dragging to quickly make a wall

Instructions

Press Left Alt (can be rebound to any key) to toggle Easy Building Mode. The building plane gets set to whatever face you were looking when you pressed the button, so if you want to extend a wall, look at that wall and press the button. If you want to extend a bridge, look at the floor and press the button. Same for a roof, railing, scaffolding, anything.

Slabs and Stairs

When you press the Easy Building Mode key while looking at a slab or stair block, it will try to match that block when placing others. This means that if you start Easy Building Mode while looking at a top slab, you will place top slabs. If you were looking at a bottom slab, you will place bottom slabs.

Server usage

This is a clientside mod, meaning you can use it even if its not installed in the server. This mod might not be allowed on multiplayer servers and could result in a ban. Please consult with server authorities before using in multiplayer.

Impossible blocks

This mod doesn't allow you to place blocks in impossible positions. It requires a neighbor to place the block against. This means that you cant place a floating top slab by placing a slab above a lone block, and you cant place blocks in the air. That said, you can place blocks you couldn't normally place (i.e. extending a bridge without peeking past the edge).