You can use a :GetPlayerFromCharacter() event when you touch the brick!
Example:
part.Touched:Connect(function(hit)
local player = game.Players:GetPlayerFromCharacter(hit.Parent)
game.ReplicatedStorage.OpenGui:FireClient(player)
end
Then just get it from the LocalScript to open the Gui and you’re good to go!
Example:
game.ReplicatedStorage.OpenGui.OnClientEvent:Connect(function()
script.Parent.Frame.Visible = true
end