[Rob_Maate]

See here: https://sampwiki.blast.hk/wiki/OnPlayerKeyStateChange

pawn Код:

public OnPlayerKeyStateChange(playerid, newkeys, oldkeys)
{
    if(newkeys & KEY_FIRE) //Or whatever key, look up the full list @ wiki
    {
        AttachTrailerToVehicle(/*trailerid*/, GetPlayerVehicleID(playerid));
    }
}

You'll need a snippet to find the closest vehicle, but I'm mad tired n im going to sleep