How do you make a fishing pole? Very important

How can you make it so once you have a tool in your hands you may click a certain brick and it will add something to you're backpack every couple seconds?

local a=0
Tool.Selected:connect(function(mouse)
	mouse.Button1Down:connect(function()
		if mouse.Target==certainBrick and a==0 then
			a=1
			Instance.new("IntValue",Player.Backpack)
			wait(2)
			a=0
		end
	end)
end)