Suki-ma
Suki-ma is a native Japanese word meaning 'gap' 
  or 'crevice' that wind, water, or light might come through. It is made 
  up of suki 'crevice, gap', and ma 
  'space', and is written in Chinese characters as   . 
The character  , 
  however, is of reasonable difficulty. Coupled with the fact that this is a native 
  Japanese word (kun-reading) and not a Chinese-style compound (on-reading), 
  there is a tendency to write suki-ma wholly or 
  partly in hiragana. Take the following example: 
    
 
        Go-zonji desu ka. Suki-ma kara shinobi-komu shigaisen 
        ni wa yō chūi.
        Did you know? You have to be careful of UV rays that steal through crevices.  | 
   
 
A Google search in August 2003 revealed the following rather confused picture 
  concerning the use of kanji and kana: 
Katakana   
  is used in specialised or abstract contexts, e.g. the 'niche' in 'niche industry'.
     The form     
  is based on the verb suku 'to be transparent,
  see  through'. (Note the form     ,
  an erroneous form based on the judgement that an optional   can
  be inserted here. This is not the case here as the character   suki is
  used for the noun only and cannot be used for the verb suku.) 
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