Good time, dear blenderartists!
As for me, the Knife Tool is one of key tools in modeling of precision objects.
In 24x knife tool works with snaps (throw Ctrl), with ortogonal projections (throw Middle button).
I cant see it in 250. I dont found it. Are there they? Help me, please. I press K and push LMB, but there is only freeform cut 
After the cut it appears in the Tools panel and shows Type to Exact. I suppose it is not coded yet because the idea is you change the Type and then the viewport changes with a Undo operation and apply the new type of cut.
Had the same problem. Only âexactâ cut available. Didnât think of looking in the tool area since I used âKâ. Then it suddenly hit me as I crawled to bed last night. MMB! The logical solution would be âexactâ on the LMB and âmidpointâ on MMB. Now, I realize that this was probably only a dream but at the time it seemed so clear to me 
The thing is, I have very little time for my hobbies (family and work and all that) so I havenât really worked myself to any point of proficiency on blender 2.3x-2.4x but with 2.5 Iâve decided to give up a little sleep each night. And it is absolutely wonderful! Not the sleep loss though, but blender 2.5. I learn things by myself with the new UI. It feels solid and professional. I very much doubt that the MMB knife cut works or will ever work (maybe I can fix that as soon as midpoint is implemented). The new UI is an encouragement to explore more than with the old UI.
âŠkeeping in mind that the knife tool will look quite a bit different with the new mesh structure (bmesh) thatâs in 2.50⊠once its fleshed out, 'n all.
apparently though bmesh project is on hold due to lack of funds: http://bmeshblender.wordpress.com/2009/11/12/status-update-5/
If anyone still wonders, i have 2.5 A2 and to âmidpoint cutâ (wich is what i was trying to do) you need to hold k+shift+drag with LMB
In Edit mode Select the faces to cut, hold down K while you shape your cut with the mouse, then hit F6 and change it to midpoints in the pop-up menu it doesnât work on the tool shelf.
Mike.
you also should read the latest blog posts and developer notes, it will be finished.
KNIFE DIVIDE!! is there a tool that splits a mesh in two at a given line?
You realise that I posted that in december right⊠I have since then read those posts and notes.
lol, my fault ^^
I discover thing similar to right solution, after 20 minutes of checking the Internet with result: none. it must be cleaned up - my English âŠbut⊠maybe someone find there key to the answer.
find boolen operation in modifiers tab in 2.53b
Try to use cuting plane - its natural knife
maybe from Mesh Tools Panel (shown/hidden with T-key) ,
button Add: -> Loop Cut and Slide,
when (A-key)ll staff is selected.
Is anybody able to tune up that steps?
Looking forward for your help :yes:
Excellent! Thatâs exactly what I needed and was looking for.
thank you very much!!!
i thought that knife tool was completely missing in 2.55 ,now itâs matter of remember the hotkeys only!!
We REALLY need B-Mesh, not for NGons, not for an improved knife tool, not so that Blenderâs modelling tools can be dragged into the 21st Century; no, we need B-Mesh so that Blenderartists isnât choked to death on new users asking âWhereâs the knife tool?â
A couple of months ago I said this would happen, and âsho-nuffâ, here we are!
Yes, we need bmesh in order to get a better knife tool. In fact the bmesh branch already have a knife tool that pretty awesome. Iâd never used the knife tool in 2.49 because it sucked, so that fact that it suck even more in 2.5 doesnât bother me that much.
For mid point cuts I tend to select edges and then subdivide. I think its a lot cleaner and more efficient than using the knife tool.
Or you could just use the knife tool and switch it to midpoints after you make your cut (hint, if youâre using 2.55, use the F6 panel instead of the last ops panel in the tool shelf⊠the bug for that is fixed in trunk, though, so if youâre using a recent build you can use the last ops panel)
@fweeb
my point is you need to select edges for the knife tool.
If your edges are already selected you only need to hit subdivide on the tools panel.
@bbrtk
You cant use a plane as a cutting tool.
Booleans require solid objects.
Use a cube, parent the cube to the object. add a boolean modifier to the object and use the cube as the boolean tool in the object drop down list. click apply.
@bbrtk @d_structorr Also you can enter edit mode select vertices from half of your object and hit P to separate.
Heh⊠that explains it. I rarely use Edge Select mode and I normally model with the tool shelf hidden.