Line

[yaser hosni]

I want plugin so that I can draw two parallel lines, with the distance between them as I want

[numbthumb]

You don´t need a plugin for that. A simple copy operation ( Ctrl+move ) with the desired dimesions in the VCB should do the trick.

(VCB - "Value Control Box", located in the lower-right corner of the SketchUp window. If you can’t see it, the most likely reason is that your SketchUp window size is larger than your available screen viewing area )

[TIG]

You can also use the built-in Offset Tool on two or move preselected edges and type in an amount to offset a copy OR offset all of the edges of a selected face by an amount.

There is also a double-line tool [dline] by Didier Bur / Jim Foltz, it's available from the crai depot http://rhin.crai.archi.fr/rld/plugin_details.php?id=804
Or in this post here http://forums.sketchucation.com/viewtopic.php?p=297720#p297720