You are taking two prices and joining them up from different times. However, your charting software, recognises that you want to join the low of one particular day to the low of another day, and then when you look on the hourly chart it has joined up those lows. But you should not expect the lines to look the same on daily.
I am not sure if I am helping here, but think of it from the software's point of view. You tell it to join up the low point on day A, to the low point on day B. That is all the info you're giving it. You then want to look at the line in an hourly chart. You didn't tell it which hour, just the day. The software can do one of two things when it is displaying it on the hourly chart:
Either
1) It can take the value of the low of day A, and assign it a specific time (say noon), and do the same with the low of day B, and draw the line between them. Note you have given the software two prices to join, but on the hourly chart it has to choose from which hourly bar this line starts.
Or
2) The software can realise that you want to join the lows up, and so it goes and finds the time on the hourly chart where that low was on day A, and finds the time for the low of day B, and joins them up.
It cannot then go back and change your daily trendline, because you drew that, and you'd get pretty annoyed if it started moving it around
So the daily line is stuck as you drew it, and you shoudln't expect this to always look the same as it does on the hourly chart.
so do and should people draw trendlines specific to diff time frames? ive heard of drawing daily trendlines and then zooming into hourly yet using the same pre drawn daily trenline.
Yes people draw trendlines specific to different timeframes, hourly is quite popular, but some people also use a 5min, or a weekly. All up to you. But yes also, you can draw the trendline on daily and go down to the hourly and look at it there, because if your software is doing option 2 (above) then it has joined up the lows on the hourly.
but it seems going in the oppossite way, eg drawing trendline in hourly chart, then going to daily, that doesnt seem to be any use does it? like a small time frame says nothing regarding the longer time frame..........yet longer frame line can give guidance to shorter time frame chart........agree?
That's a more general quesiton than just trendlines. I wouldn't say the shorter timeframe says nothing about the longer, but I would agree that the longer timeframes are more significant, if that is what you mean.