(CNN) -- As you prepare to board a plane for a holiday trip, you might be asking yourself if you should check things or carry them on board.

Because of a new crackdown on carry-on baggage, the decision may be made for you when you arrive at an airport security checkpoint.

United Airlines and Delta Air Lines have installed baggage templates at security checkpoints in airports around the United States. Delta has put them in about a dozen airports, and United expects to have templates installed in 60 airports by early 1999.

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"We think it'll do the thing we want it to do , which is to improve on time departure performance and also create a hassle-free environment in the boarding process for passengers," said Joseph Hopkins, a United Airlines spokesman.

Solid, over-sized items that don't fit through the 9-by-14 inch (23-by-36 centimeter) opening in the template will have to be checked. But, large items that are soft are likely to make the cut as carry-on baggage.

Car seats and medical aids such as crutches are exceptions to the rule.

Critics insist the new system will cause new problems.

"One is that there are going to be increased delays at security as people are caught unawares by the fact that they can't get through with a larger bag. Two: There's a question as to whether or not the airlines are going to be able to handle the increase in checked baggage," said Chris McGinnis, a business travel consultant for CNN.

Continental Airlines has filed a lawsuit against Delta over the templates. The two airlines share baggage screening devices at San Diego International Airport, along with Frontier Airlines and America West.

The suit filed Monday alleges that the equipment has created traffic jams at the security checkpoint and forced some Continental customers back to the ticket counters to check their bags.

"Continental customers shouldn't be penalized by Delta's imposition of its unfriendly baggage policies," said Mark Erwin, Continental's vice president of airport services.

Continental said any restrictions on the size of carry-on baggage should be managed by individual airlines. The airline also said it is expanding overhead bin space in more than 150 airplanes.

The lawsuit seeks an injunction and unspecified damages against Delta.

Delta spokesman Bill Berry said Continental agreed last spring to have the equipment installed and even paid part of the $3,000 cost. He said Delta has received few complaints from its passengers and no complaints from Frontier or America West.

Based on a report from CNN's Business and Travel and Beyond. The segment appears weekdays on Early Edition at 7 AM (ET) and on Morning News at 10 AM (ET).