Look at these:
|Actually we call these 'CARRIAGE' Bolts - the gif is from the UK where they say things differently.|
Their diagrams are super clear and informative too - like this one :The website is called technologystudent.com - it contains numerous information sheets and exercises to enhance the study, understanding and teaching of DESIGN and TECHNOLOGY. I enjoyed visiting each section too because they built gif files for everything! They were fun to watch and I even learned stuff.