how can you create a killbrick?

(Those blocks that kill you when you touch them)

fairly simple:

script.Parent.Touched:connect(function(hit) -- gets the killbrick, and runs this code when it is touched
	if hit and hit.Parent:FindFirstChild("Humanoid") then -- finds out if it hit a humanoid (aka character NPC or other model with a humanoid)
		hit.Parent.Humanoid.Health = 0 -- kill
	end
end)

this script should be in a part

EDIT: A bit more information. The way killbricks usually work is to first use a Touched connect function to detect when the killbrick hits or is hit by another part (on line 1) afterwords, it finds out whether the thing that hit it was part of a player (not the player object) and then changes the player's humanoid health to 0, killing it. Note: you can change values other than Health:

hit.Parent.Humanoid.WalkSpeed = 50 -- superspeed!

or

hit.Parent.Humanoid.JumpPower = 200 -- super jump!

Well, it's really simple really. First you must have a brick, and add a script inside of this brick.
In the script you'll need to add this line.

script.Parent.Touched:connect(function(hit)

end)

this says 'when this brick is touched something will happen'. Now we need to add a few lines checking to see if what is touching it is 'alive'.

script.Parent.Touched:connect(function(hit)
	if hit.Parent then -- new line that I added
	local hum = hit.Parent:FindFirstChild("Humanoid")  -- new line that I added
	if hum then  -- new line that I added

else  -- new line that I added 
	print("Not human")  -- new line that I added 
		end -- new line that I added
	end  -- new line that I added
end)

What I just did checked to see if one, the part was touched, and if whatever touched said part has a Humanoid inside of it, otherwise it will print to the output/console that it isn't 'Human'. Now what we need to do is well kill it if it is human.

script.Parent.Touched:connect(function(hit)
	if hit.Parent then
	local hum = hit.Parent:FindFirstChild("Humanoid")
	if hum then  -- new line that I added
		print("Is Human")  -- new line that I added
hum.Health = 0  -- new line that I added
else
	print("Not human")
		end
	end
end)

Now if it is human, it will put in the output or console saying that it is human, and then kill it as well.

Now remember next time, not to ask us to make a script for you, that is not the purpose of this website, our purpose is to HELP you with your script that YOU have already attempted to make. As the name is ScriptingHelpers and not ScriptCreators