I already post this topic in Blockhead forum ,link at below vv
http://theblockheads.net/forum/showthread.php?4782-Tips-Build-Metal-Base-with-1-steel-block
But now that thread is disappear.
I'm not sure it has been removed or something ,and I already sent report to administor.
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note: I'm not good in english ,sorry for that ;v;.
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I have 2 method to do this, but I choose one easiest way to do.
This way it'll use only 1 [steel block] and wooden[trapdoor] (many as you want)
Before that, you should know how trapdoor works.
follow my thread:
http://theblockheads.net/forum/showthread.php?4778-Tips-How-does-Trap-Door-works
or
http://ninsect.blogspot.com/2013/07/note-i-backup-this-topic-from.html
1. place [steel block] at high as you want
2. put other block below 1 level (like picture) length as you want
3. make roof with [Trapdoor] put from near steel block.
4. break those other block.
(now trapdoor roof will not function at all ,nobody can pass it)
5. now you can place trapdoor anywhere in that steel background.
you can use trapdoor to make wall, make sure that have enough space for put [Iron trapdoor]
Enjoy :D