This is a collection of 3 nice commands I often use.

1. CA: copy objects in an array-like way.

I like using this instead of the array command. In most simple cases it works. You can create an array of grid lines, or rebars, etc. at various spacing using this command.

2. RA: This is similar to CA command, except now you are rotating objects.

3. 7BRPURLINS

This command is for steelwork. Select purlin lines and enter lapping length. The code will automatically find crossing lines (they can be columns or beams or trusses) and break each purlin at every intersection point, extending each purlin to both sides at a distance exactly equal to your specified lapping length.

More interesting, run this and select purlin lines once again, but now enter the new lapping length. It still works!

Note:

• the spacing between 2 purlins is scaled to your current dimension text height.
  
  
• to have your column or beamlines auto-selected, their linetypes should be continuous.
  
  
• in the screenshot, I lock layers except for the purlin layer. Therefore, I can select purlins quickly by 1 crossing window.