How to place a block perfectly next to another block?

Hello, I made two scripts where you can place blocks around the world (or something) and stalked with one problem. You can't perfectly place a block next to another block. In my opinion, it creates big trouble. How can I solve it? Here are these scripts: (The placement aside which I tried to make, is located in the local script, mouse.Move function)

Local Script:

local tool = script.Parent
local rs = game:GetService("ReplicatedStorage")
local event = rs:WaitForChild("BuildEvent")
local block

local rotation = 0

local createBlock = function()
	local newblock = Instance.new("Part", workspace:WaitForChild("Folder"))
	newblock.Size = Vector3.new(4,4,4)
	newblock.Anchored = true
	newblock.CanCollide = false
	newblock.Transparency = .5
	newblock.Name = "Block"..math.floor(math.random())
	return newblock
end

tool.Equipped:connect(function(mouse)
	block = createBlock()
	mouse.Button1Down:connect(function()
		if mouse.Target then
			event:FireServer(block.Position)
		end
	end)
	mouse.Move:connect(function()
		wait()
		if mouse.Target then
			mouse.TargetFilter = block
			if mouse.Target.CFrame.LookVector then
				block.CFrame = CFrame.new(mouse.Target.Position) + Vector3.new(4,0,0)
			elseif (-1 * mouse.Target.CFrame.LookVector) then
				block.CFrame = CFrame.new(mouse.Target.Position) - Vector3.new(4,0,0)
			end
			if mouse.Target.CFrame.UpVector then
				block.CFrame = CFrame.new(mouse.Target.Position) + Vector3.new(0,4,0)
			elseif (-1 * mouse.Target.CFrame.UpVector) then
				block.CFrame = CFrame.new(mouse.Target.Position) - Vector3.new(0,4,0)
			end
			if mouse.Target.CFrame.RightVector then
				block.CFrame = CFrame.new(mouse.Target.Position) + Vector3.new(0,0,4)
			elseif (-1 * mouse.Target.CFrame.RightVector) then
				block.CFrame = CFrame.new(mouse.Target.Position) - Vector3.new(0,0,4)
			end
		end
	end)
end)

tool.Unequipped:connect(function()
	block:Destroy()
end)

(Server) Script:

local rs = game:GetService("ReplicatedStorage")
local event = rs:WaitForChild("BuildEvent")

event.OnServerEvent:connect(function(player, pos)
	local newblock = Instance.new("Part", workspace:WaitForChild("Folder"))
	newblock.Size = Vector3.new(4,4,4)
	newblock.Anchored = true
	newblock.Name = "Block"..math.floor(math.random())
	newblock.CFrame = CFrame.new(pos)
end)

Thanks in advance.