Ok, Great, it was Osnap that was on not Ortho, when I clicked it on and I checked and it indeed did come on in the options page. I will read the notes you all sent about the snapping. cheers, D
Because that controls grid snap, not object snap. With your setting you can only place something at a point on an imaginary grid with intervals of 0.5mm in the x,y and z directions. So you can snap a point at (51.0, 1.5, 7.0) say, but you cannot snap one at (51.0, 1.4, 7.0). Grid snap often gets in the way, because things don’t conveniently start or end exactly on the grid. Which is why @Helvetosaur asked you to turn it off.
To control the object snap sensitivity you need to change
which relates to pixel distance on your screen, not distance in your model. 15 is the default and I find it works fine on, say, a 3000x2000 pixel screen.
Here are some examples of things turned on and off
The 22.5 degrees figure in your illustration says that when you have the Ortho constraint turned on you can only draw lines in sixteen directions (On a compass rose N, NNE, NE, ENE, E, ESE, SE, SSE, S, SSW, SW, WSW, W, WNW, NW, NNW, there being 22.5 degrees between each of these bearings). If for some reason you only wanted to draw parallel to the axes you could set this to 90 degrees.
Grid Snap is evil, unless you’re actually using it for something at the moment.
OK! you folks are really helpful. I looked over your pics and made sure mine were the same. I had changed the grid snap to .5 so I changed it back. I understand the rest of what you are writing, more or less. Yes, grid snap can be evil if you aren’t careful, but I was using it the other day and it worked for what I needed. I WILL keep it off unless it has a direct use. This program has so much potential that is is kind of overwhelming, but I will perservere. Thanks to all, cheers, d