Constrain global Z axis transform / Solid or Wireframe toggle

`Z`

All hotkeys for Blender

General Bounding Box Center pivot	`,`
General 3D Cursor pivot	`.`
General Select all / Deselect all	`A`
General Active Object pivot	`Alt` + `.`
General Play animation toggle	`Alt` + `A`
General Isolate 3D view toggle	`Alt` + `B`
General Linked Duplicate (Instance)	`Alt` + `D`
Object mode Reset location	`Alt` + `G`
General Unhide all	`Alt` + `H`
General Delete keyframe	`Alt` + `I`
General ...to <keybs>9</keybs>: View layer 11 - 20	`Alt` + `0`
Editing mode Proportional Editing connected toggle	`Alt` + `O`
Editing mode Unpin vertices (UV/Image Editor)	`Alt` + `P`
General Play animation in reverse toggle	`Alt` + `↑ Shift` + `A`
General Orientation menu	`Alt` + `Space`
General Solid / Textured toggle	`Alt` + `Z`
General Border select (marquee select)	`B`
Sculpt mode Clay brush	`C`
General Add Subsurf modifier with that # of levels	`Ctrl` + `Num 1` - `Num 9`
General Median Point pivot	`Ctrl` + `,`
General Individual Centers pivot	`Ctrl` + `.`
General Move camera to current view	`Ctrl` + `Alt` + `Num 0`
General Link file	`Ctrl` + `Alt` + `O`
General Make Proxy	`Ctrl` + `Alt` + `P`
General Quad View toggle	`Ctrl` + `Alt` + `Q`
General Set Origin menu	`Ctrl` + `Alt` + `↑ Shift` + `C`
General User Preferences window	`Ctrl` + `Alt` + `U`
General Render animation	`Ctrl` + `F12`
Editing mode Vertex Groups menu	`Ctrl` + `G`
General Select Inverse	`Ctrl` + `I`
General Screen presets toggle	`Ctrl` + `← →`
General Lasso select	`Ctrl` + `Mouse movement`
General Mirror object over an axis	`Ctrl` + `M`
General Turn selected object into active camera	`Ctrl` + `Num 0`
General Back view	`Ctrl` + `Num 1`
General Other side view	`Ctrl` + `Num 3`
General Bottom view	`Ctrl` + `Num 7`
General Open file	`Ctrl` + `O`
Editing mode Make Vertex Parent	`Ctrl` + `P`
General Quit Blender	`Ctrl` + `Q`
General Save File	`Ctrl` + `S`
General Make Parent without Inverse	`Ctrl` + `↑ Shift` + `P`
General Redo	`Ctrl` + `↑ Shift` + `Z`
Editing mode Mesh Select Mode menu	`Ctrl` + `⭾ Tab`
General Save User Settings	`Ctrl` + `U`
General Maximize current view toggle	`Ctrl` + `↑ ↓`
General Save File	`Ctrl` + `W`
General Undo	`Ctrl` + `Z`
General Transform Manipulator toggle	`Ctrl` + `Space`
Editing mode Extrude region	`E`
General Open file	`F1`
General Show last closed rendered image	`F11`
General Render current frame	`F12`
General Save As	`F2`
General Repeat History menu / Save Rendered Image (UV/Image Editor)	`F3`
Sculpt mode Grab brush	`G`
General Hide selected / Minimize node toggle (Node window)	`H`
General Frame all in view	`Home`
Sculpt mode Inflate brush	`I`
General Save last render (Render window)	`J`
General View layer 1 - 10	`Num 0` - `Num 9`
General Increase 1 frame	`←/→`
Object mode Move object to a different layer	`M`
General Properties panel toggle	`N`
General Frame selected in view	`Num .`
General Global/Local view toggle	`Num /`
General Active camera view	`Num 0`
General Front view	`Num 1`
General Rotate view up/down in iterations	`Num 2`
General Rotate view up/down in iterations	`Num 8`
General Side view	`Num 3`
General Rotate view left/right in iterations	`Num 4`
General Rotate view left/right in iterations	`Num 6`
General Perspective/Orthographic view toggle	`Num 5`
General Top view	`Num 7`
Editing mode Proportional Editing on/off toggle	`O`
General Rotate	`R`
Sculpt mode Smooth brush	`S`
General Maximize current view toggle	`↑ Shift` + `Space`
General Add menu	`↑ Shift` + `A`
General Scale Texture Space	`↑ Shift` + `Alt` + `T`
General Marquee zoom / Set render border (Active Camera)	`↑ Shift` + `B`
General 3D Cursor to origin	`↑ Shift` + `C`
General Duplicate	`↑ Shift` + `D`
Sculpt mode Brush strength adjust	`↑ Shift` + `F`
General Link/Append from Library	`↑ Shift` + `F1`
General UV/Image Editor	`↑ Shift` + `F10`
General Text Editor	`↑ Shift` + `F11`
General Dope Sheet	`↑ Shift` + `F12`
General Logic Editor	`↑ Shift` + `F2`
General Node Editor	`↑ Shift` + `F3`
General Python Console	`↑ Shift` + `F4`
General 3D view	`↑ Shift` + `F5`
General Graph Editor	`↑ Shift` + `F6`
General Properties	`↑ Shift` + `F7`
General Video Sequence Editor	`↑ Shift` + `F8`
General Outliner	`↑ Shift` + `F9`
General Hide unselected	`↑ Shift` + `H`
General Arrow Go to end start/end frame	`↑ Shift` + `←/→`
General Snap menu	`↑ Shift` + `S`
Sculpt mode Flatten/Contrast brush	`↑ Shift` + `T`
General Search (3D view) / Toolbox (UV/Image Editor)	`Space`
General Object Tools panel toggle / Toggle frames or seconds (Timeline)	`T`
General Object Mode / Edit Mode toggle	`⭾ Tab`
General Increase 10 frames	`↑ ↓`
Editing mode Rip selected vertices / Set Handle Type menu (curves)	`V`
General Constrain global X axis transform / Delete menu	`X`
General X Constrain local X axis transform	`X` then `X`
Editing mode Split Vertex / Edge / Face	`Y`
General Constrain local Y axis transform	`YY`
General Constrain global Z axis transform / Solid or Wireframe toggle	`Z`
General Z Constrain local Z axis transform	`Z` then `Z`
General View all layers	`~`
Editing mode Close / Open a curve	`Alt` + `C`
Object mode Clear rotation	`Alt` + `R`
Editing mode Shrink / Fatten	`Alt` + `S`
Object mode Remove selected from active group	`Alt` + `↑ Shift` + `G`
Editing mode Reset Tilt (Curves)	`Alt` + `T`
Object mode Apply menu (such as freeze transforms)	`Ctrl` + `A`
Object mode Allow selected to render	`Ctrl` + `Alt` + `H`
Editing mode Hooks menu	`Ctrl` + `H`
Object mode Join selected objects	`Ctrl` + `J`
Object mode Make Links menu	`Ctrl` + `L`
Pose mode Recalculate Roll menu	`Ctrl` + `N`
Object mode Make Dupliverts Real	`Ctrl` + `↑ Shift` + `A`
Object mode Add Constraint menu	`Ctrl` + `↑ Shift` + `C`
Object mode Add selected to active group	`Ctrl` + `↑ Shift` + `G`
Editing mode Tilt (Curves)	`Ctrl` + `T`
Sculpt mode Layer brush	`L`
Sculpt mode Pinch/Magnify brush	`P`
Editing mode Select Similar menu	`↑ Shift` + `G`
Object mode Select Linked menu	`↑ Shift` + `L`
Editing mode UV Mapping menu	`U`
Editing mode Specials menu (varies per object) / Weld / Align menu (UV/Image Editor)	`W`
Editing mode Extrude menu	`Alt` + `E`
Editing mode Fill create faces	`Alt` + `F`
Editing mode Convert selected triangles to Quads	`Alt` + `J`
Editing mode Merge menu	`Alt` + `M`
Editing mode Beauty Fill create faces	`Alt` + `↑ Shift` + `F`
Editing mode Select linked flat faces (Face Mode only)	`Ctrl` + `Alt` + `↑ Shift` + `F`
Editing mode Edges menu	`Ctrl` + `E`
Editing mode Faces menu	`Ctrl` + `F`
Editing mode Extrude / Create new component or bone	`Ctrl` + `Mouse left click`
Editing mode Loop Cut	`Ctrl` + `R`
Editing mode Edge Flip	`Ctrl` + `↑ Shift` + `F`
Editing mode Recalculate normals to inside	`Ctrl` + `↑ Shift` + `N`
Editing mode Vertices menu	`Ctrl` + `V`
Sculpt mode Brush size adjust	`F`
Editing mode Knife cut	`Mouse left click` + `K`
Editing mode Knife cut midpoint	`Mouse left click` + `↑ Shift` + `K`
Editing mode Crease / Set Keyframe Extrapolation menu (Graph Editor)	`↑ Shift` + `E`
Editing mode Proportional Editing Falloff type toggle	`↑ Shift` + `O`
Editing mode Select Row from selected vertex (NURBS surface)	`↑ Shift` + `R`
Editing mode Warp	`↑ Shift` + `W`
Pose mode Remove IK constraint	`Ctrl` + `Alt` + `I`
Pose mode Add IK menu	`↑ Shift` + `I`
Sculpt mode Draw brush	`D`