A tool that automatically lays blocks and walls?

I have seen an item in-game several times but thought nothing of it. The item was meant to automatically lay block. Another was used to lay background. I cannot seem to find them now that I want to see what they do.

What do they do, and how do I obtain them. Does anyone know what they were named?

Solution 1:

The Traveling Merchant sells the items you are looking for, though none of them automatically take any action (excepting the Paint Sprayer). Instead, each item increases the speed at which your character lays blocks / walls. They each cost 10 gold and are sold randomly (the merchant may not have them in stock each time he visits).

• Brick Layer - increases the player's placement speed when placing blocks, furniture, and any other placeable items
• Portable Cement Mixer - increases the speed a player can place background walls
• Extendo Grip - extends your block mining and placement reach by 3 tiles
• Paint Sprayer - automatically applies paints to objects when placing them (requires that paint be in the player's inventory in order to function)