If you find a symbol you don't recognize, look for it in the LEGEND at the front of the book (assuming NACO, I don't know from Jepp, but there's probably one there too).
The "lightning bolt symbol" is the Glide Slope Intercept Altitude.
The PCG says:
-harryGLIDESLOPE INTERCEPT ALTITUDE- The minimum altitude to intercept the glideslope/path on a precision approach. The intersection of the published intercept altitude with the glideslope/path, designated on Government charts by the lightning bolt symbol, is the precision FAF; however, when the approach chart shows an alternative lower glideslope intercept altitude, and ATC directs a lower altitude, the resultant lower intercept position is then the FAF.