Minecraft 1.7.10 and down does not have a built in invisible block. This is InviBlock for Minecraft 1.7.10
The inspiration for this was the floating candles at Hogwarts. These invisible blocks are very simple. They have no texture and are solid. You may pick them up when breaking them down. They do not leave a shadow or emit light. The selection outline does display as with any other solid block when you point directly at it. They are simply invisible but solid.
You may place torches on them or use them to hold back liquids. You may use them as invisible walkways or walls. These can keep monsters away but you could still see them. You can make an invisible ceiling to keep the rain off an area. You may apply this block to the Carpenter's Blocks as a texture, making them invisible. Mods such as openblocks or microblocks that use a saw can cut the invisible blocks into thinner or smaller pieces for special projects such as keeping project red's red alloy wire separated, or even pipes separated and still look good. If you have ender IO's painting machine you can paint glowstone with this making it an invisible light source.
The recipe is one glass above a cobble or the reverse.
This is the simple invisible block.
For something more complicated you may want to check out this other mod by someone else
You may use this in modpacks and redistribute this with credit where it is due.
Liscense is Creative Commons Attribution
INSTALLATION
Drop this into your mods folder and restart the game as usual with forge mods.
NOTES
The source code is included in the jar file.
This does NOT affect world generation.
Have fun!
PS: Thanks Talsera for the nudge that got me to do this.