Hello,
the map work was going sweetly untill a red line came out of nowhere and the map is leaked now and i cant compile it :

can you tell what is this and how to remove it please. thank you
Hello,
the map work was going sweetly untill a red line came out of nowhere and the map is leaked now and i cant compile it :

can you tell what is this and how to remove it please. thank you
Well obviously your map is leaked, so fix the leak, and it will go away.
Follow the red line to the outside of your skybox, and patch it up.
Chances are you shifted your skybox a unit, so there is a gap in your map.
That red line will show you where it is, Follow it and fix it =)
i tried but i cant select the line and the line is not related to entity on the map. please help
other info. this line appear once i try to compile the map the first time then it keeps showing
You may have deleted some brushes which formed an entity. But the entity settings still exist.
Press L to list entities and find one you thought you deleted or select each one in turn . The one you cant see selected in red outline is your culprit, press back space to remove.
the easiest way to find the leak is to goto the entity where the redline starts in the 3d window and follow it while it twists and curves around brushes… eventually you
will see where the redline exits to the outside of the map, you probably just shifted a structural brush by mistake.
Yes, just follow the red line in the 3D window and eventually you will end up somewhere where the red line will go out into the grey/black “void” (emptyness). Your map should not leak into the void. If you follow the red line and you see the leak, move some brushes or make some new ones so the red line cannot go trough to the void anymore, then compile again and do the same untill you red line shows up anymore.
If you notice your red line going through a brush, that brush is a detail brush. Detail brushes don’t stop VIS (the red line can go trough them) so you might want to make that particular brush structural (Ctrl+Shift+S)
OK, the problem is that the red line is not related and does not lead to any entity on the map . i created a structural brush to block as you suggested but the line still continu.im really afraid that its a big problem. spent a hundred on this map and once again im blaming myself for not backing up the .map file so plz help me.
oh and im not that big mapper, so can you tell me what SHIFT A brush means?
problem solved, i ahve made detail my skybox which caused that problem but i still have 2 questions :
What does Shift a brush means ?
and another ord that i am too familiar with and still dont know what it means : LEAK. what does mean an entity is leaked or whatever is leak and how to fix it?
thanks lot you nice people
“Entity leak” means that an origin of an entitiy is inside of a structural brush.
This can be ignored (reading some information here in the forum).
But you can’t ignore a normal “leak”.
Normally a map has to be sealed.
It’s not allowed that there is a connection from inside the map to the outside that contains nothing (void).
You can create a box out of six brushes which create a hollow box.
And inside of this box you can create your map.
shifting a brush isnt a mapping term, it’s simple english 
it means moving a brush, or… making it bigger you could say in radiant terms… (“pulling out” one side of the brush)
anyway i simply meant that you should close up the gap if there was one, either by shifting (moving) or creating a new brush…
and always remember to filter detail brushes off (ctrl D) when your chasing a leak to avoid your mistake.