Number Lines In High School

  I just tested my Pre-algebra class on integers and they are still struggling with negative signs.  Based on the answers I checked, the kids see the problems in one of two ways.
A.)  They do not recognize the negative sign with a negative number so they treat everything as positive.
B. ) They do not understand what the integer calculations represent.

With this, I am going to reteach it next week before I introduce variables.  I am seriously considering having the students create a number line that resembles a slide rule so they can put the window on the first number and then slide it left or right based on the second number.

I found an activity for making a slider using a zip lock bag but I'm afraid it looks too  "elementary".  I want it to resemble a tool so they won't feel as if they are being treated as elementary students.  I did a search for instructions so that on Monday my students can make their own.

I looked at several images and finally found one that looks like it will work.

 I cut a shoe buckle looking  slider out of an index card.  This will allow students to create the number line they need.  Once they've made the appropriate number line and they can thread it through the slider.  They put the first number in the middle of the slider and then move the strip left or right the appropriate number of places.




You can see how it might work in the picture below.

 I am going to have students make these on Monday so they can use these with a worksheet of problems.  I'll let you know how it goes.

Just in case, I did find a web site with an interactive  number line where you input the ends of the number line and it automatically creates a number line which you can then use to solve a problem. You can choose to count by any number be it one or 20.   Unfortunately, it requires flash so it cannot be used on an iPad. You could use computers.