For dual-ended direct-wired LEDs, line is connected to the lampholders at one end of the fixture, neutral at the other end. Shunted or non-shunted lampholders can be used with dual-ended LED tubes. Dual-ended tubes can be reversed in a light fixture just like a fluorescent tube. When using non-shunted lampholders, the wires only need to be connected to one side of the lampholder with most LED tubes (check the wiring instructions).
LED Direct-Wired Dual-Ended Wiring Diagrams
Using existing light fixture wiring
Using new 18 AWG light fixture wiring and non-shunted lampholders