This is the type of trailer power jack that is permanently fixed onto the trailer. Either via welding or securely bolted on the trailer's A-frame tongue. It generally has a lift capacity of 2,000 to 5,000 pounds.
A-frame jacks are the most popular type among electric trailer jacks. That's because a lot of trailers in the market has an A-frame trailer tongue. It is structurally stronger than other types of trailer tongues. So for safety purposes, people generally prefer to get A-frame trailer tongue & jack.