NOTE: this is capable of killing most things except big game, so DO NOT attempt to shoot anyone or anything without thinking of killing it, and if you do, I am most definatley not responsible for the death or injury so be-friggan-ware.
Also note that the crossbow should be made over a span of 2 days, the second day can be spent assessing the crossbow, tweaking it and adding features.
Step 1: Materials
-Ratchet saw (that motorized hand saw thing)
Note: if you do not have this you will be sore from cutting the wood out with your hands, so yeah, this tool helps.
-Coping saw (any saw will do)
-Vice (absolutely, positively needed)
-Carving tool (last picture), fairly useful, if you can get one.
Note: I have gone into detail, just in case some idiot complains about it.
Deadly Resources required:
-Wood (1 metre length and 15 cm width, which is about 3 feet length and 6" width, I think).
-String (strong, the thicker the better)
Note: Wooden blinds can be substituted for bamboo, I will go into more detail in step 3.