using a take out double over an opening bid
The take out double is not exactly an artificial bid except that it was not designed to be used in this context. The bid of "double" normally indicates that you think the opponents will not make their contract and if they don't they get severely penalised. If they believe they can make it they can "re-double" which gives them a shed load of points if they make the contract.
The doubled bid has been adapted over the years and there are now lead directing doubles and others beyond the scope of this website but the one that is arguably the most useful is the take out double.
Check the hand shown here. Twelve points, enough to open but the opponent in front of you bids one heart. You don't have a decent suit to bid but you could support ANY suit your partner were to bid so you say "doubled". When the bidding gets around to partner they bid their best suit in the full knowledge that you can support it.
It works really well but there are a couple of things that can go wrong. Once you have doubled, what happens if the next bidder re-doubles? That would give the opponents a game contract even though they only played in one heart! This places an intolerable pressure on your partner as s/he MUST BID even without any values in their hand.
The other thing that can happen is that your partner may have a hand containing a lot of hearts, (opponents suit). In these circumstances it is in order for partner to pass thereby converting the take out double into a penalty double.
The ideal shape for a takeout double is 4-4-4-1 or 5-4-4-0 with only one card, or a void, in the opponents suit. Some players bid a take out double with two cards of the opponents suit but that's asking for trouble if you and up in a high level contract.