One of the most useful things about extension cords is that you can quickly make one long cord from two shorter ones. Connector compatibility is all that is necessary, and that is usually not a problem, at least in the United States.
While this may work for a short term need, it is not a good solution for long term use.
If you find yourself regularly having to link extension cords to get power to where you need it, or if you are linking extension cords for outdoor use, you should really consider investing in a cable that is the right length.
In addition to having to worry about the cables becoming disconnected, linking also creates a shock hazard.
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