The 2dFillet tool in my 2dTool set works in 3d too, if also has a 'chamfer' toggle, if you fillet two lines with 0 radius it acts like trim/extend tool. There's also 2dAdjust that lets you pick several edges/arcs as targets and then several more to 'adjust' to the targets - either extending or trimming the line/arc as appropriate... There are also several other 2dTools in the fill set that mimic CAD like 2dHatching, 2dLineStyle and 2dText... My Mirror tool allows you to mirror a selection about any point/line/plane - it has some advantages over the Scale tool with '-1', or the flip-on-axis methods from the context-menu, as you can chose to make a copy as you Mirror - just like in ACAD. To tidy messy edges/gaps etc 'OpenClosedLines' is available at Smustard.com [$?] An alternative is to look at Thomthom's 'Cleanup' and 'Edge' tools ['free' - see Plugins Index link above...] which do various things that might also help... His 'guide_tools' also let you add cpoints in various ways. There are tools to add cpoints by picking points and of course there is a midpoint snap inference for any edge, so you can place a cpoint at the midpoint of any edge [if there's no connecting edge then draw a temporary line between the two points, snap to its center for the cpoint location and then erase the unwanted line]; however, if you must have this as a separate tool then http://www.smustard.com/script/Midpoint is a free download that adds this to the context-menu... You change the current axes using the Axes tool - this is equivalent to making another 'UCS' - you right-click context-menu over an axis to reset back to the 'world-axes'. Sketchup isn't CAD so you need to appreciate the differences - the main one is that Layers do not separate geometry - they simply show/hide what's on them; so draw all connected geometry on Layer0, make a group or component and give that a different layer so that if is seen/unseen. Other non-connected geometry is made in a similar way so you get no unpleasant surprises - separating say a face and its edges by layer is very risky as erasing a visible edge can also erase an invisible that that needed the edge - because you can't see geometry on another layer doesn't mean it's not reliant on some geometry that you can see and will can be affected by your editing/erasing of that - unless you use group/component to somehow separate this geometry and you then use layers to control visibility of those... You can also lock/unlock groups/instances so you can't accidentally edit, move or erase them - another usefu'