Commands:

check save - Save your current position
check load - Teleport to your saved position
check undo - Teleport to your previous position
check stats - Display your stats to everyone
check reset - Respawns you and discards your checkpoint data

Short commands:

/s short for /check save
/l short for /check load
/u short for /check undo 
/r short for /check reset 

Notes:

There is a delay of 5 seconds between saves and loads, to prevent abuse of the commands.

Binding keys to commands can be done by typing the following in your console:
bind <key> "say /l" | e.g. bind "p" "say /l"

If you leave the server during the game your checkpoint data will be saved for your return.
Note: This data is discarded after mapchange.